there is no servo tray. all control surface servos are mounted externally at the control surface. (well, i guess you could consider the mounting area the tray)

anyway, on my ucd46, that area is fine, no problems whatsoever. firewall is also strong. problem areas have been the dowel at the root of the wing coming loose, landing gear block breaking several times, even after initially being reinforced (landing gear itself is plenty strong), and problems breaking the horizontal stab from the fuselage. (reinforce this one well!)