Joe are you absolutely sure you got your dimensions right?
This Galazan reproduction Trojan Butt Plate, albeit with slightly smaller dimensions than what you posted, worked perfectly as a replacement for my 12-ga. 2-frame Trojan. Galazan says theirs is made from hard rubber just like the originals were. When I was in the market for a reproduction butt plate I found that other suppliers were using hard plastic rather than hard rubber.
http://www.csmcspecials.com/Parker_T...te_p/pb310.htm