Developing a design....... ah, the joys of designing.....

Don't have much time but having done more than once the math you need done...... Off the top of my head, every ounce you remove from the empenage on a 70" long model will let you remove about 2.75 ounces from the front. If you only move the weight (as you've mentioned by moving the servos) you're looking at about 2 ounces for each ounce.

So move the two servos to the CG and you can figure on losing about 9 ounces.

Shorten the tail around 2" and you'll get about the same.