I had to pick between a bigger, more expensive glory hole from a known brand or a smaller, cheaper one from a local guy. I went with the local one to save some cash and support a small business. It heats up fine, but the opening is a bit tight for some of my bigger pieces, you know? Anyone else run into this and find a good way to work around it?
Actually heating the glory hole collar first like hall.ruby said is the better approach here. Getting the edge to expand before you try the fit means you're not fighting against the piece itself getting soft and floppy. Extra heat on the piece can actually make it harder to guide in straight since it loses its stiffness.
That "opening is a bit tight" sounds frustrating! @caleb_bell's idea about extra heat is smart, but have you tried warming the glory hole's collar itself a little first? Sometimes just getting that edge to expand slightly makes all the difference for a tricky fit.