There are ways to make the vulcanized material work out.
a few tricks I use- glue the liners to the scales first, with one of the no line adhesives. a slow cure CA or gorilla glue work out well- or one of the loctite 300 series. THEN cut to shape and sand a bit with a very crisp belt and slow speed. once everything is FLAT for the glue up to the knife, glue up.
At this point I generally (since I do more forming after glue up) grind some shape into my scales and blend the tang in with 60 and 120 grit belts. then I do a lengthwise run with 220 grit by hand. This tend to get all the issues taken care of in rounding the handle and cleaning up the spacer material- which isn't going to "bleed" much as it's one piece with the scales before you glue up the knife. THEN I run some super think CA along the spacer areas and let it soak in and dry. back to the belt for slow 320-400 work and finish by hand (usually to 600, but whatever floats your boat)
One last thing I do is apply a curing oil. Linseed requires the most soaking and time, or tru oil, or whatever. I even do this on my micarta handles.
For whatever reason in the above processes, I have as yet (know on wood) had very little trouble from the vulcanized material.