Rocker arm shaft replacement Mazda

1991 Mazda B2600
Replace valve seals. Need to reinstall rocker arms shaft assembly.

This model has 12 valves and 10 (5 pair) bolts holding the over-cam rocker arm shaft to the cylinder head. The rocker arms slide back and forth on the shaft probably 10 thousands of an inch.
Don't want to force anything, but am having trouble lowering the shaft assembly on to the head and having all 10 holes in assembly and head line up. The holes have and indexing projection (10 total) and while the bolts do enter and the threads start by finger (up to a point) I am reluctant to put a wrench to the assembly. Note that there is still about a 1/4 inch gap between the shaft assembly and the bosses on the cylinder head.
Should I not be able to push this all down by hand instead of by tightening the bolts with a wrench. The arms are not under tension yet and have considerable play.
Anybody done this? Any advise?

Thank you!