Ok, so there are no rules, but you know there are fans out there who have rules about repaints and follow them.
It's simple. Follow the known plastic layouts.

What happens when you have a modded toy? Is that rule totally out the window, or does it just get modified? Maybe just make some substitutions when there's no obvious reasons for things being separate/together. (like slightly softer plastic for thin parts with a lot of stress on them going together)
I just realized by habit that I was following the old rules on this repaint idea even though I was taking the top half of one figure and the bottom of another, and adding a new head. :S I imagine if Hasbro did this, there's no question it would be a 100% new mold, even if it was the same design. (it's Cybertron Hardtop's top, on Energon Barricade's bottom)

Thems some big freakin' legs on tiny ol' Hardtop!

To answer your question, it depends on what I think about the custom I'm working on. Classics Sunstorm, I pretty much followed the mold breakdown, because I wanted him to fit with the other Seekers. Classics Siren though, I ignored the breakdown and painted to match the homage best. As for modded figures, those I almost always ignore the mold breakdown.

There's the line between the speculative redeco, where yea, you would want to follow the mold pattern, and a proper custom where anything goes. Paint where and what you want, how you want. Mods make no difference in the case of an actual custom.

Nah. Not so much. Not when he compacts his legs. Chunky, yes, but at least he's not a towering giant.

(Storm Jet got the same treatment. zig-zagged elbows, and compacted legs)
GUESS WHO! The molds are all related.


Well, yeah. Straight repaints are totally different. They're either plausible as real products or they're not.
I guess other than the purple bits, I should ignore the plastic layout. (which means shoulderblades and the strip on his torso)

Liokaiser.

Did you already know because you read the other threads? :>

Yup.

I look forward to seeing how it turns out.

There are no rules. You paint what you want, where you what, how you want. Hasbro and Takara break mold layouts all the time by covering entire parts in paint.

Do note, though, that unless you're in the habit of using primer on everything (which in and of itself doesn't solve all problems, either), sometimes your own ideas will be limited by the base plastic colours, too. Trying to paint whites and yellows over dark colours is, of course, a nightmare. And then of course, when you're dealing with toys with as many joints as TFs, you're bound to encounter paint rubbing in areas with tight tolerances, so if possible, it's always best to optimize your colour selections beforehand. Balljoints are a nightmare. Some people have taken to dying problem parts like that, but that comes with its own set of limitations.

For example, I'm working on the last stages of finishing up a Classics Thundercracker to complete my Seeker six-man team. While most of the figure is Classics Starscream with the paint completely stripped (also a smart thing to do when doing a major repaint, as sometimes the colours/textures from the base paint can still show through, causing other problems. The first time I attempted Thundercracker, I didn't strip the paint, and I needed so many layers of paint to completely hide the wing markings that I started to lose detail, and a few areas started to look gloopy. So then it was back to the drawing board, this time going for as thin a layer of paint as I could manage), I opted to use forearms/feet from a spare Classics Ramjet instead, so that I'd have a darker base colour to work with so that if the paint got scratched, it wouldn't be as obvious. Additionally, I decided to leave strategic areas of those parts unpainted gray, so that there'd be no paint wear at the hinges, but also as a stylistic choice to create some visual interest.

It's all turning out pretty well so far, I just have to devise some wing markings for him. Surprisingly very little paint rub, despite the mold's rather tight hinge joints. The paint's holding up well, I don't even think I need to use a sealant. I should strip the paint from his knee joints, though. I misguidedly hoped that the paint would take in those areas, but of course it didn't, and the paint rub looks a bit unsightly to my perfectionist nature.

yeah... if you're doing it yourself, you imagination is the limit... as long as its paint you're using

some of the Dyes don't always work the same... variances in the plastic, or occasionally almost identical different plastics will react entirely different.

if you're using dyes then yes, just to eliminate one more variable I'd go by molding...

but... I'll go along with what ever anybody else says if they will custom me this

Cybertron SPREME!

Hah! I totally forgot about that! >_<; Thanks. Yeah. Not sure I could paint his purple parts off-white. :S (or actually, it might be unpaintable plastic)
Jaruga seems to have two stripes of purple on his upper chest, but I think that's only his breastforce beast companion. Ah well.

Try a basecoat of gray/silver first, as that can help decrease the bleed-through effect, if necessary.

And AFAIK, there's no such thing as truly unpaintable plastic (minus the stuff used for soap bottles, but that's not exactly relevant). It's just that the factory paints don't take well to the stuff.

What paint is best for Hartops legs then? I've added some acrylic detailing to Swindle and Hard Top. Yet I always wanted to do a complete repainting of the purple with a purple paint ot look less Plasticy. So I was wondering if anyone has an idea of what adheres best to that plastic.