I forgot all about the sphere and printed the 'Helix challenge' to see if I could get some good 3-4cm bridges. ( http://www.thingiverse.com/thing:4659 )

Good to hear that the ducking adapter worked, sad to hear your PSU died though ;o
Don't you have sunken screw holes in the Aluminum plate? that would solve the issue of the bulldog clips.

I will print a full sphere (without supports/raft) tonight - I think it will be doable - and make some pictures together with the double helix outcome.