CW---re OS bearings---I'm a bit surprised at the short life you've had from the OS 160's stainless rear bearing.
I don't keep the meticulous records that you do,but mine last a lot longer.
I use similar fuel, the same props, in a pattern model of much the same weight.
One difference though----when first starting to use the 160 two or three years ago, we found it a good idea to decompress the motor quite a lot (head shims totalling 30-40 thou.)
This actually increased the top end rpm a little (kept adding 10 thou. shims until no increase),and gave a nicer, softer, sound. There was a slight slowing of the transition from idle to low midrange, but this could be alleviated with a small "bump" on the Tx throttle curve.
Just wondering---might this slightly lower compression ratio help with rear bearing life?