I recently rewrapped my
PR-10 bar with fizik microtek, and could NOT get the fizik plugs (which aren't particularly attractive) in... hammer, spit, young muscle. Nothing. I only had one of the plugs from the bike in pre-restored condition-- pretty sweet looking, with a swirly/whirlpool end-- that fit with much pressure.
In the end I did a little reconstructive surgery on the plugs: filed the inner part down, clipped them in a way to let the four quadrants compress more effectively, and finally did a little sanding. Took about 5 minutes for each plug, and it still took a hell of a lot of jamming on-- but it worked. And they're not coming out without another struggle.