Flush Mount PMC IB1/2 any experiences ?

Hello Dear Forum Members, this is my fitst post in this great forum. I have spent some time reading and can find some very useful information & hope i can also give some of my knowledge if possible, I am currently building two studios. One for mastering, other mastering/mixing with a professional acoustican. Both studios should have flush mounted speakers. Currently i own PMC MB2s (passive & free standing) and plan to buy another pair of them or IB2s (passive). I know MB2 work well flush mounted but i have so far not seen the IB2 in such a configuration. They are a bit smaller but in my opinion have the better/faster bass. Max SPL is 116dB, MB2 = 124dB. So the IB2 can be eventually be a bit so quiet for a heavy damped room at a distance of about 2,5 meters. So soffit perhaps helps a bit regarding the max SPL in the Bass. So my questions are : 1. Did anyone flush mount IB2 ? 2. As IB2/MB2 are passive is it possible to change the corossover regarding the shelving filter or can this only be done externally ? (Full active is too expensive for me, sorry !) thanks for you help greetings Andreas