i actually just put a patchmeyer (spelling?) grip on my P99 and had it there for about a week. I took it off because it added too much to the grip and it no longer had the 'poured into my hand' feel that the bare grip has. I may try the small patches of griptape strategically placed for comfort without compromising the look.
I also found that I did not have a need for any kind of grip until I started into the warmer weather, and now my hand gets real slick after a few rounds. Whether I find a fix or not, I will not let a small thing such as this effect my feelings towards this incredible piece of machinery
I recently did the innertube thing, which is nice because you can choose the width. The only thing is, at least with the tube I bought, it has a bit of a sticky feel to it, which was annoying. That decreased after one usage so maybe it will go away, we'll see. If you do this buy one for a skinny-tire (10-speed type).