The aspect ratio would increase, of course, but it would be nothing like that of a motor glider.

Since the taper remains the same, the wing area would not increase very much, therefore the CG would not have to change much, or alternatively, the tail volume would have to be slightly increased, either by a slight lengthening of the fuse or a slight increase in stab area, or a combination.

If the plane is currently balanced conservatively, as is often the case, then it's possible nothing would have to change at all.

The roll rate would decrease, but that's not necessarily a disadvantage. Models generally roll much faster than full scale anyway.

The thinner airfoil would have some consequences, depending on the choice. But it's not like the design of a Yak 54 is cast in bronze, or necessarily the best possible proportions at any scale. What did you have in mind with your change?

Jim