the change from EJ22 to EJ25 is an increase in both bore and stroke. Infact, the EJ25 is the only newgen engine to have a different stroke. All the rest are 75mm with just different bores. Anyway Like others have said throw in some EJ22T pistons to get the compression down. I do wonder however, if pistons are all that's required to lower the compression Or if they'll even lower the compression. There could be a difference in deck height, or head gasket thickness, or something that'd prevent the EJ22T pistons from being effective. Like lets say for example the EG33 and EJ22 share the same dimension of pistons, yet the reason the EG33 has a much higher compression is from a thinner headgasket or something, so even putting those pistons in wouldn't do anything. Really that's all speculation though.

About the mounting of turbos, wouldn't mounting them too high just create too much heat too high up in the engine bay? I still personally think a single turbo would be a much easier and better way to go about this. Maybe you should consider that? A nice semi large turbo like a TD04-18G/20G or something?