do the conversion, then re-balance it. You're going to rremove some hardware from the nose, right? The nosegear, pivot, pushrod.....less stuff also means less stuff to break. You're gonna add a little weight in the tail. It will need rebalancing, but it must be rebalanced on the original point of balance! That's what makes the thing fly right, right?

As far as flying ability, it'll quite probably fly a little better, but I don't think it will be all that noticeable on a trainer. You're going to remove more weight than you put back on, so the plane will be lighter by an ounce or two.

Just ensure the CG remains the same!

For what it's worth, the maingear should be ahead of the CG, but not by much. Take a look at a Cub for the relationship - those are good handling taildraggers. Take a look at a traditional old-timer to see a BAD relationship. That's the way they built them back then, but that doesn't make it right - those planes weren't meant to be ground-handling queens, and with the gear that far forward they weren't. (personal experience speaking). If you want to personally experience groundloops on takeoff, put the gear up there.........