Looks like a simple solution. Simple is good.

I'm curious about your 76mm aluminum barrel. I ordered one from MK Modellbau since Axel's Modellbau was out of the Schumo 76mm barrels (which are now back in stock). I assembled the kit barrel to compare the two barrels because the aftermarket barrel I bought was vastly larger than the kit barrel in circumference. I'm guessing you had to enlarge the hole for the barrel since it looks to me like it is larger than the kit barrel? Which barrel are you using? My research indicates that the KV-1 and the T34/76 guns were basically the same, but they had a different designation.