All the BRCA legal cells should be a height similar to Sub C cells diameter however they will sit on top of, rather than "in" the chassis slots on most saddle pack cars. This should mean that all that is required is to lift the battery strap posts by at most the thickness of the chassis however many people are adding the weight under the cells (getting it as low as possible is important to many).
The kit Fabs has designed for the FS is by far the best I've seen for any car as it takes much as much of the weight as he could and transfered it to the centre ridge of the car between the cells, meaning that only the minimum extra weight has to go into the cell 'tray'. The only thing I would have done slightly differently is to have the cell straps made out of a heavier material (such as brass) rather than put it all in the 'tray' and have carbon straps. Here is my logic. The way in which the car rolls, and thus the way the grip changes through the corner via the geometry, will be effected by the centre of mass of the car as a whole.
As the LiPos are much lighter than the sub Cs they are replacing and you are putting the mass back under the cells you are effectively lowering the centre of mass of that section of the car. If you were to take the extra mass and devide it equally between above and below the cells you would be raising the centre of mass slightly as the whole assembly is sitting "on" rather than "in" the chassis as the sub C cells would. A little bit of maths would quickly tell you how to devide up the additional mass to give you the same height for the centre of mass.
Now, what Fabs has done is move some of the mass between the cells and on top of the chassis plate. This will combine to give the nearly correct effect as the car rolls (can't see how it can easily be bettered in the space available under the shell).
So Fabs set is the best currently available but is there a better way ..... yes, run the type of cells the car was designed for ... NiMh, hence why I am doing everything I can to stay with NiMh until such time as there is a chassis set out there designed around the mass of Lipo cells
Guess who is not feeling particularly like concentrating on his job this morning
