QUOTE(Destron D-69 @ Mar 16 2012, 09:45 PM)
looks okay, how secure are the connections?
Not at all, For the BTS and G3 trailers. As mentioned above, they're designed soley to snug over that rectangular plug on Classics Prime. In G3's case, it's just a hollow circle ridge of plastic that's as wide as the plug on Classics Prime is long, allowing it to fit over said plug and rotate around it. BTS's is a bit more complex, with an actual rotating adapter inside their socket. If someone wanted to make an adaptor with Shapeways that'd work all around, it shouldn't be too hard. (rectangular plug socket on top, 5mm-ish rod under it, with a thin wider disc of plastic between them)
The Trilogy/Chronicles trailer hitches as well as the DOTM Deluxe prime; Round peg on trailer goes into round hole in hitch.
I will point out that the Chronicles trailer has clearance issues if you're trying to turn; As in, the corners of the trailer do not clear the back of either Optimus' cab (or in the PRID mold's case, his shin-cover joints).
PRID is a bit too big, really. his wheels are a bit bigger, and he gives the trailer a slight tilt as a result.
But I'd say it's a better match than the 3rd party trailers. The DOTM Voyager's trailer might be perfect, but that's just a guess.