Why would you go for U47 amd not U87?
dont know, i haven't worked with any of the 2, but i had a quick listen at a u47 replica at a friends studio, and it sounds good.
its just from what i read on the internet i suppose, the way the mic was used on kick drums and stuff on the beatles records.
i will probably never build one, but then again, you never know what the future holds.......
but the first thing now is to try and find those Transound TSB-165A capsules, and see if i can get something working.