I know this thread is a little old sorry about this but i have a nitro pede also i was modding. I put a 1200mah rx pack xip tied up front on the body post and added a slash 2wd front bumper incase i wanted to add some wheel weights to it which would have held it down better. a .28engine is a bit big but do able thats for sure congrats on putting such a large engine in there. adding maybe a proline runtime tank if you can mount it right making a mounting plate to use the same holes as stock will add a little more weight to the center which i added for longer runtimes and a 2.5R engine. add some larger wheels also like 3.2's or 3.8's but you have to use 17mm adapters. there is a thread on traxxas.com in the nitro pede forum there someone used 17mm hex's all around give a look.