FT_TC3Racer - I had been racing my FT TC3 straight out of the box for a few months at the local track and was running mid-pack in the Stock A main several months ago. I was driving well, but was not fast enough to win. I read some good things about the BMI chassis from others on this site (BMI thread) so I ordered one (one-way was added too).
The only drawback that I see currently is the chassis does not accept the larger IB3800's (I use GP3300). I have tried the new cells in another car, but I continue to race my TC3.
The BMI chassis gets a decent portion of weight out of the car, and the batteries are moved much closer to the centerline which helps it transition very quick. The chassis is extremely firm and works great on the high traction surface I race on using rubber tires. The change for me was very noticeable, and I think you will find the same. I have no affiliation with BMI, and I no longer run mid-pack.