Not junk! Second best improvement i've done to the old panhead. The first being Russ' RSES. Electric starter.
The sleeves are stiff and they grip the nipples and manifold well before the clamps are installed. Use your carb as a fixture to ensure the manifold is indexed correctly before tightening the clamps.
Regarding the clamps
I installed them loosely and then applies air at 10 psi. I slowly tightened them until they sealed. I then performed the bubble test. You don't have to use brute force on the clamps.