Thanks for asking!
I use spring pins for alignment because they will never loosen, nor do they deform the mold when pressed in, whereas solid pins have both problems. Springs pins are not precision IN THEMSELF, like ground pins would be, and for this reason, I handscrape the sockets to insure absolute precise alignment, more precise than any other method of alignment.
The deep engagement which I insist on is what causes you problem in closing the mold tightly. I do this so the mold alignment will never change or wear out for most customers, IF A DAB OF MOLD LUBE IS APPLIED REGULARLY TO EACH ALIGNMENT PIN! (Same for under the sprue plate out at the end where the spring finger holds it down, and on the pivot screw area. The best mold life I have had reported to date was 400,000 bullets from a four cavity, which was returned to me out of customers pride in it's performance, It was still casting round within .0002 inch. Half the thickness of saran wrap!
Being a bit pig headed about quality I set myself this standard way back when I started making molds, 27 years ago, and use it with all my products. -- If there is any problem with what I make it gets reengineered and the change incorporated in all future products, immediately! A couple of bullet designs were yanked instantly, when I got bad reports, back there in the beginning. Though I still had them in the catalog till my stock of catalogs was used up, I refused to make them.
So, you'll see no blush when I claim LBT molds are the best made in the world.!