The link on the first page has a bit about balance.

The prototype apparently had about 6lbs of batteries under the canopy area. Roughly looking at it, I would say the engines may be a foot behind the c.g. with a couple of feet available in front of the c.g. Therefore, for each 1lb added in total motor/fan weight you would need another 1/2lb or so in the nose to balance. I am guessing that you could get it to balance with the heavier motors but I would personally go for the lighter option. I understand that the latest lay-ups that Chris is doing are lighter but the prototype was 24lbs which is reasonably fat for its size.

Model A-10s are generally notorious for balance as they don't have a huge cannon in the nose to help out. I am going to try to save every ounce at the back end to make it as light as possible. I was even considering removing the starters from the Wren 44s to help out but will probably sacrifice this for ease of operation. I have the added 'problem' that I won't have 6lbs of batteries on board to balance it all out.