[Def]

You've got it all wrong - IWGs control high boost easier. Low boost on a "large" engine needs lots of flow area. High boost is cake to hold, especially if you're not going to run really high turbine inlet pressures - which rotaries do not tolerate at all (which is why people run huge A/Rs and deal with lazy spool and run low boost).

The BW EFRs have plenty of WG flow area to run >15 psi or so on a reasonably sized engine, and even low boost on most engine sizes as well. You just need the proper spring rate WG canister and the proper amount of WG canister preload.

IWGs do have issues - on piston engines with a "small" turbo on an engine it's keeping the boost up when the turbine inlet pressure rises and forces it open. But that's almost a problem of too much valve area for your WG canister pressure/preload.

A lot of the IWG problems you see are there are because people are stupid and do things like run 0 mm preload on the WG canister rod then complain of lazy boost pressure (minimum preload is 2 mm, something like 4-5 mm is more reasonable).