With the exception of the 35% Sukhoi, engine side thrust is built into the firewall at the factory. This is why the assembly instructions state to use equal length standoffs and to drill the mounting holes square to the firewall. Depending on how tight the firewall fit the manufacturing jig the thrust angles will fall between 1 and 2 degrees, with the majority at 1.5 degrees. Wood density and moisture levels effect the fit of the part to the jig.