Here's a nice option for adding weight to your ride when running lipo packs.
The plates are the size of common car packs (@136x46mm) and also half size 23mm strips to fit on the sides of a battery.
4 ounce plates (4.25 oz) are 1.7mm thick
2 ounce plates (2.25 oz) are 1 mm thick
1 ounce plates are .5mm
Depending on which lipo you have, you can run the plates under the battery or beside or both.
There will also be a 46x23mm size to fit in front or behind a battery.
Several guys ran with them at a big race last weekend where lipos were finally allowed!!!
Check out here for some pics etc... www.teamfusionracing.blogspot.com