Here is the airfoil '.gif':

http://www.aae.uiuc.edu/m-selig/ads/afplots/sg6042.gif

It would appear from the '.gif' that the CG could be set somewhere between 1/3 of the cord and 40% of the cord depending on how you like it to feel while flying and landing. 40% might be the limit and maybe 38% back would be a better maximum if the plane still behaves. However I bet that 1/3 of the cord would handle very well for a stable camera platform.

I would assume the CG for your 'pusher' would be the same as for a 'tractor' arrangement since your horizontal control surface will be behind the wing (typical).

I would start by setting the CG at 1/3 of the cord with no fuel and try small changes in CG over time to see if there is any advantage to moving it back.