For slothead and anyone else who is interested here is a bit more info on how i modded up some sport track straights to fit into the humpback bridge sides so that i didnt need to use a convertor staight.
1 remove all the steel track by carefully bending the metal tabs out. i use a flat head srewdriver to do this as i found it kept everything flatter.
2. store all the little bit safely to avoid being annoyed later.
3 using a scalpel carefully cut small v grooves in the bottom plastic surfaces (see photo 1)
photo 1
repeat the pattern at the other end. when cutting the v's on the sections where the track runs only cut down through the bottom most section not all the way as this would weaken the track too much. On the other ribs i cut all the way to the bottom surface of the track.
4. Once that is done the track is flexible enough that you can bend it well enough to work out where to cut small notches for the lumps on the ends of the sides to fit. (see photo 2)
photo 2
be careful to only cut the notch out of the very edge section as the inner one is needed later to hold everything together.
5. once all the notches are cut get out your heatgun and start to warm up the areas that need to be bent working in strips across the track. This bit was a bit of trial and error but with a little patience eventually the shape should look something like the bridge. Better to bend the track a little past what is required as this will allow the track to sit flatter when finished.
6. once i had done that the most challenging part is trying to shape the rails. In the end i just used my thumbs to bend the rails very gently a little bit at a time. once the first one was the right shape it was easy to math the others to its shape. (be careful to get the orientation of the rails correct)
7 refit the rails into the track. I used a screw driver again wedged between the rails and then another to flatten the little tab around the track.
8. Attach the sides to the track. if you have cut the notches at the ends accurately it will actually stay together quite well. but i used a dremel to drill a small hole through a little dimple hole in the sides right through the inner rib on the track and then slid a dressmakers pin into place to hold it all together (see photo 2 again)
9.paint to desired effect if desired
10.race!
