The grabhandles are for the infantry to grab when riding the tank, so thinking about this when you are making/remaking them should help you envision how big they should be.
Also, the only problem you have right now, and I know it is a major kit failing but I wanted to just bring it up, is that the turret under the mantlet is all wrong. There should be no undercut under the mantlet. Tamiya really screwed it up. And the turret is too "thin". It should be about 1/8" thicker/taller. This is NOT to discourage you at all, you have done some darn fine work on the kit to really bring it up to standards, but I wanted to let you know about the turret issues before someone mean and nasty came along...