I have gone 136 mph @ 7000 rpm with a 29" tire that probably is about 29.5 to 30" tall at that speed which comes out to 5.1 to 6.9% slippage.
I have used nitrous to go 144 mph @ 7500 rpm which is between 6.3 and 8.1% slippage.
Do these numbers look ok? I don't know what is typical.