Tannoy HPD 15" flush mount or not?

[tomasz]

My friend has a pair of old Tannoy HPD 15inch drivers that he was thinking of flush mounting in his newly built studio. I could not find any solid info online but I was hoping maybe someone here could give their opinion on those speakers. Are they usable in this application and if yes how to? Where can I get construction plans on flush mounting speakers in the control room. Any other recommendations for known flush mountable speakers and construction plans on how to do it? Thank you
tom