Just thought I'd post my lipo mod.
I started by grinding off the cell cradles with a Dremel in order to get a nice, flat base that would let the lipo hardcase sit as low in the chassis as possible. This took about 20g off the chassis and didn't increase the flex at all.
I made a plate to sit under the battery from 2mm brass plate which adds back 60g (which I need to get the car back to legal weight).
The brass plate puts the weight just about as low in the chassis as it can go.
I still use the stock battery strap, but I used a belt sander to grind off the arched cell holders, so I can run it with the Tamiya logo up.
I also sanded the top off so I didn't have to raise the battery posts.
Now the battery sits low and it's all good (note the brass plate in the motor access hole in the chassis side).
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I'm happy with how this worked out - obviously not Tamiya legal, but it helps me try to keep up with the Xrays and the Corallys
My next mod will be a couple of thin slots in the chassis base so I can run battery tape instead of the strap - should be a bit more secure and help to keep sideways movement to a minimum.
Let me know what you think.