Just a correction but team 1625 has used a custom chassis for both years of its exsistance. Here's the link to the picture our 05 chassis
http://www.chiefdelphi.com/media/photos/20834
and there is no good picture of our 06 chassis
I would like to add that custom chassis take a lot longer than kit chassis but our 05 chassis gave us a really really low center of gravity and that helped a lot. This past year it was made to fit what we needed and it worked excellently. Lucky for our team we have an amazing ex-engineer who can aluminum weld very well. Without him we would have probably used the kit chassis. We also have some pretty nice prototype drivetrains that have really nice chassis.