Krammer - I know the VMARs are not that great a plane but I have never heard of them being tail heavy. You have to hold the plane upside down to test the CG. For such type of planes I would have about 15mm on low rates and about 25mm on high, I usually go for almost whatever is mechanically possible to high rates.

When you say go vertical for 2 secs then it comes back down it may mean your engine is not powerful enough to hold the plane in a vertical, what prop are you using and what RPM are you getting?