I did beta is20 work with George. I did a dyno run with Very conservative settings. Lower peak boost (about 17) than I was getting with is12, but holding a couple psi more on top.
240hp with 300ft at the wheels.
After that I added boost to peak at 20 and hold out 4-5psi average more than is12 on top end. The logs looked great and and more is on the table.
Winter came, so no dyno run on those settings. But I see no reason why they wouldn't be more than 250hp.
My feeling is that 250-280 wheel is possible depending on supporting mods.
The real story, even at 240hp, is the extra top end. Even at 240 wheel, I was making more power everywhere with almost no loss in the bottom and a huge gain on top.
The is12 and jb1 would taper down to 9psi on top. I have the is20 and jb4 tapering to 14 now. 5 More psi all the way to redline!
It felt real good even at 240hp.