The alu battery trays... yes drilling those big holes did save me a few grams (and I agree it was a waist of time):
The cut out was needed to make room for the center transmission. On my previous E-Sav I had put washers in between the bat trays and the chassis to make room... but I wanted to skip that on this one.
The whole thing from another angle:
This has cost me a few hours of work... the materials can be found pretty cheap either at your local metal shop/smith or at a DIY retailer.
I know its nothing special... but I think its important to show that it doesn't have to cost alot to do a conversion. I'll update if/when I break anything ;)