I agree on the flexing... David... but where these are run - the way this subframe is made (a TCI unit) there won't be any flex right there - and it's sold mounted to the body - no rubber... so in THIS instance I felt I could get away with the cleaner "double 45's" which will allow some flex but not like the double 90's would do.
This sub is solid mount to the body - no bushings - and has the additional "up the front of the firewall" mount point. Pretty solid I think. <keeping fingers crossed>.
My Nomad has a double 90* --- for the very reasons you mention!
You can barely see the brake lines in this photo --- but they head out the master - take a 90 to the firewall - then a 90 back to the front before then drop... basically an "S".... but that frame is rubber bushings...