Need some more information. How many RPM do you get spinning the 20 Hydro? How fast are you currently going? Does it ride bow high or stern high (hydro's normally carry the stern if I remember correctly)? How is the handling?
Labbing a prop usually gives you another 200 rpm or so... but if you are already at redline with the 20 Hydro, you might have to have them add an inch of pitch when they lab it to bring the rpm's back down, which results in more speed.
There are some merc. dealers who have specially painted (blue) loaner props. Or ask some of your friends with performance boats if you might borrow their prop for one spin around the lake. I'd think that if the 20 hydro works, you might like a 22 Merc. Bravo One prop (especially a labbed one).