Mine has the T-tail, i.e., the elevator control runs up the front and over the top of the fin, and is attached to a control horn on the top of the elevator. I haven't really seen many Seamasters recently, so I probably missed whatever evolution may have taken place, but I just did a Google and saw something that must be what you are referring to.

The snap behaviour you describe doesn't sound to me like tail blanking - but I am no expert. Blanking of the tail, one would suppose, should lead to loss of elevator control, initiating either a deep stall or porpoising. In a deep stall, either the CofG is sufficiently forward that the plane eventually drops its nose and unstalls the tail and recovers, or you manage to power out of it - or if the CofG is much too far back it would probably flat spin.

Any planes I have had which are set up to be highly aerobatic and/or control sensitive and/or have an aft CofG are practically guaranteed to snap upon sharp elevator input. That's what I would expect, and desire.

From your description, why don't you simply reduce your elevator travel, or consider putting perhaps -30% or such exponential. The latter will give you less twitchy response to a large range of stick movement, but when you REALLY want it, you will have that full deflection, AND NOW!

Experiment a bit. If you don't have a programmable radio, you can still get some of the exponential effect by using a servo arm that is not the 90 degree setup. Think about it, make a little drawing, and/or try it on the bench with your model. You will be trying to make the one direction (up elevator) less sensitive around neutral, but the other direction will become more sensitive, so think it through!

Another thought is to adjust your ailerons (flaperons, if you have them set up that way) to either droop slightly or to be raised just a bit. That might make a difference.