Well, I haven't tried Wayne's version, but I have been brewing my own with Vytaflex 30 for a while now.
I my experience, if you race at a club (long straights), then the 30 will need gluing in every case.
They also wear very very quickly. I wore a set down to almost nothing just practicing at Wolves Le Mans race in the spring.
I used another set recently at a vintage 1/24th race in Belgium on a gloss track and they too wore very thin after 8 segments.
I dread to think what the 20s would be like.
As for grip, Vytaflex 30 has a little more than some Ortmans but a little less than some others (depends on what vintage Ortmans you have).
At Wolves, they have less grip than the NSR, on our club track, less than Slot It 22.
At the same vintage meeting, we raced 1/32nd on a Carrera track and the difference with NSRs was about 0.8 second a lap, 0.4 with the Slot It 22 (12 second lap).
For me, I find grip is OK for general use, but the wear rate is too high, especially on an abrasive track. I will try the shore 40 once I run out of the 30.
The best thing is that by brewing your own, you can restore any old vintage car you want for very little cost.
Joel