I found one of the VQ ME-109 build threads for you, here it is:
http://www.rcuniverse.com/forum/m_69..._ME-109/tm.htm
In this thread the aileron servos are mounted out in the wing and drive the ailerons directly. Is yours not like this? Perhaps there is a hole for mounting that is covered over and you simply need to cut away the covering and mount the servo. It should be just ahead of the aileron.
I'm not familiar with JR servos, but standard size/power servos should work fine. Something around 35 - 45 oz. of torque. As for flaperons, you don't want to do that with 'barn-door' type ailerons. With both ailerons dropped for a 'flap' configuration the wing will be MUCH more likely to have a tip stall. This is where the tip of the wing stalls before the root does, causing the plane to flip over and dive into the ground just as you are about to land! No fun!