Ipurchased it a while back, and I tried to put the appropraite parts onto my Collectors Club Topspin. When I did so, and I may be wrong at this part, are the legs of Topspin supposed to face the same direction? If so, then what might be wrong with it?
AFAIK... there should be NO differences between the Energon/ROTF and Timelines combiner copters. There's also a number of pictures featuring Nexus Prime using pieces of both FP sets without much issue. Example: Nexus Prime as Upgrade Fansproject Bruticus | Flickr - Photo Sharing! using the FP redecos of Blastoff/Swindle, and the timelines bots.
there's a tab on the side of the legs that the slot in the forearm slides over, if you need a pic, i can try to get one for you
I know what you are talking about, but the tab on his legs, both face in the same direction, so I can only attach the forearm securely if one leg faces backwards. Any ideas?
Sounds like your Topspin has two of the same lower leg. If you got him directly from the club, contact them about a possible replacement, explaining you just now noticed the problem.