"taller" gas checks

[BD]

Anyone know of a method or source for gas checks that are" taller", meaning that they cover slightly more length of shank? I'm having issues with fliers in the .450 B and there's some evidence that the heel of the boolit is being cut by gas as it goes by the gas port. My concern is that the gas is getting around the gas check as it passes the port.
BD

[RU shooter]

If your making your own its as simple as using a slightly larger blank(disk)

[Doc Highwall]

You will have to make sure that the shank on the cast boolit will let you seat the gas check with out hitting the bottom driving band.

[BD]

Is anyone selling a .45 cal die that would let me do this? I'm no machinist.
BD