I order to fix the rear deck down without using the 6 screws I have fiited a bracket to one of the stretcher bars and threaded the spacer for the vent. I can get at the wing nut to fix it by opening the 2 rear hatches and it hold it really firmly. Means I can fill the 6 screw holes now.
I was thinking not to bother with fixing it but I have had the turret on the Panzer nearly fall off after a rough traverse of some logs so it was a bit of belt and braces I guess and I couldn't be doing with undoing 6 screws and also the look of it as well.