Ways to protect MMM when used with subpar batts

Please don't chew me up too much for asking this...

I've tried to do my homework, doing searches and readiing posts, etc. I understand that Patrick recommends the biggest, baddest, batteries on the planet. However, I'm not after an extreme setup, or to do any racing just yet. It's just that I can't go out and drop more $$$$ for new batts right away. So, I'm trying to figure out how to run what I have for a little while, if at all possible.

The posts about Castle's new insert said to use mild gearing. Check.
The deal with hard braking causing voltage spikes which pop the FETs is not something that I think will be a problem for what I'm doing. (I hope.)
So, that leaves voltage stress taking out the power supplies...

One question there is which of the 3 blows most often. I'd suspect it's the BEC since that deals with the most current. As a result, I wonder if using a external one (or an Rx pack) will offer additional protection.

Anything else, I've left out?

For reference, I'm not running a huge MT. It's an RC8E/MMMv3 2200, on a medium-sized indoor "stock slash-friendly" track. I have run it out there a little bit already with a 15T pinion, motor timing set to 0, and 100% punch control, and it wasn't bad. My goal would simply be to have some fun with it without shortening the life of my controller.

Can I get away with it, or not? Thanks!