[Andy A.]

Be aware that when you start adding weight to an R/C car, you have to start making adjustments and upgrades to suspension, motor, gearing, speed control etc. R/C cars are not made to carry a lot of weight.

There is a fine line between using a R/C car saving you development time and money and the modifications and hassle of the premade stuff slowing you down.

Just keep that in mind. I've been involved in a few R/C car to robot projects and in the end we've always scrapped the chassis in favor of custom stuff. Usually, the only usefully thing at the end of the day are transmissions and suspension. Weight is you're absolute enemy if you don't want to do any hardware modification.

Good luck!

-Andy A.