As in the case of a multiple or double iron molder, I find it
best to insert the iron in the rear section before the front.
If I am only adjusting the iron, I will still usually remove the
front parts totally before adjusting the rear, and then finish
up by replacing the front.

I rarely find it necessary to strike the body of a molding plane
to adjust the iron position. Or should I say with enough force
to mar the wood. Twin Irons would never be adjusted that way!