Weakest link - Bailey BOV?

It's been suggested my Bailey BOV is struggling to maintain boost and is leaking boost to aomosphere under load.. this may be a reason I'm not getting full power from the boost/fuelling I'm running..

Car runs an almost constant 1.2 bar with 1.25 peak at 4000rpm - hisses loudly under load...

How easy is it to swap the spring, insert shims (not my choice) into the BOV. My worry with shims is if they break or are sucked back into the engine..?

It is better to change to an HKS BOV etc..?

questions, questions..