Photoshop :: Photoshop 6.0 - Weak Registration Marks

I am using a plugin for Color Separation named FastFilms which produces separated (hidden/non-modifyable) color channels. When I print any channel (to an old 11x17 HP Laser 4V) using 300 DPI, the registration marks are nice and dark, but of course I lose pixel definition. When I change the print setting to 600 DPI, I get more pixels but the registration marks are much lighter and partially missing parts of all the circles.

I am using this for screenprinting and the light registrations do not expose enough to print. Eliminating the Plug-in as the problem, I created a totally new blank page and printed (same printer) in both 300 DPI and 600 DPI and (hard to understand), both prints have the lighter registration marks.

Unless I can somehow darken the registration maks (during print), it would also work if I could "unlock" the hidden Photoshop separated channels (for each color from the plugin) and copy/paste duplicate manual registration "+"s myself. Manually prepared graphics with manual registrations work fine on this printer. I am at a real impass on this. Any help, suggestions, or ideas?