Eny has zero impact - plenty of good stuff still available with a 29 eny - which is where it's capped, iirc. 
Maybe adjust the ENY of troop carriers to (literally) slow down the horde.   

M-3  48mph;  SdKfz 251  33mph;  LVT(A)2  24mph.
All are currently ENY = 40.
If M-3 ENY = 16;  SdKfz 251 ENY = 22;  LVT(A)2  ENY = 26.
population    ENY     troop carrier
16  9  6       15.8     all available
16  7  6       16.2     251 and LVT available
19  7  6       22.4     LVT available
24  9  6       29.0     fly a goon    
