Chris,
Obviously I'm biased but the way I have mine (or the mirror with a 3 gear) seems best. 6 cells across the back is just wrong in my opinion
where as the cap weighs hardly anything so no probs with it out there. Some run a PT in the 6th cell place the other side though I have mine on top of the servo. I do remove the height of the plastic chassis rail at the back of the speedo (where the wires are) for a little more room.