Hello all.
Donīt have the Stalker 51, but like my 46 likes more 11x6 than 12x6, I could imagine yours could be happier with 12x 5-6, at least will worth to give it a try.
The ground RPM might be between 8.200 and 9.000, on a fast 4 stroking or a wet 2 cycle.
Hope it helps.
Please let us know the result of the experience!!!
Regards.