HS-425 would be more than strong enough for this plane. Warbirds don't really put that much stress on a servo.
I am sure others will dissagree especially when it comes to servos but I have been using JR-537 standard ball bearing servos for over 2 years now in this plane and would not change. Well over 75 flights on the first one I built and now about 15 flights on the new plane using the same servos.

Randy