Tim,
How did you install the phenolic mount? If you screwed it to the end off the old wood mounts ( ala Tom Morris), it should be good. If you only epoxied it like a former I would add "L" clips bolted from the wood mount to the mount ring. Reason I have a friend who lost the nose a couple times from an epoxied mount. I have one on a Tutor II with a 3/16" plywood front mount that bolts to the original wood mounts with three clips, one on each side and one at the bottom through the plywood doubler, this one also has a rear bearing support ( ala Bob Hunt). The other is in my Stuka and is epoxied to the thinned down mounts then because my friend had the epoxy fail I put the small wood screws in the sides, hundreds of flights, on problem.
The mount needs to be as strong and stiff as if it were an IC. Early on it was thought because there is less vibration we didn't need as strong a mount, some used 1/8" plywood, this allowed flexing and the ship could do funny things, especially in the wind. A strong mount or addition of the rear external bearing solved this.
As far as grinding down the mounts more, it's just to save weight.
Best, DennisT