Arm Board levelling: is this good enough?

Certainly. I don't know whether a digital inclinometer can really be trusted to be accurate to 0.1°. The armboard was made by Lee Drage at Acoustand, so it should be well made. I chopped it up to repurpose it, and any errors will be related to my mounting it.

More important is that the arm board is in the same plane as the platter surface. If they are both off perfect by the amount shown, you are more than good enough. Even a little more error from true horizontal could be tolerated if the platter has a like error.

Coming from an almost cost no object tooling and measurement background ( think F-22, B2… etc ) I doubt  your tool. I agree w Lew on seeking same result from platter and armboard . Finally, I love your posts and adventures with multiple arms and pods. I just added a 2nd Brinkmann Bardo and am also working an arm pod DIY project. Best in music to you !!!!!

jim

If the inclinometer is off, at least it confirms the platter and the armboard are parallel.

The thing that surprises me is that all three agree with each other and the platter!

I'll get around to doing the other table one of these days.

The most important thing is that it sounds good.  Remember your records themselves are not all perfectly flat either.  Being off by such a small amount is insignificant given the overall vagaries that are inherent in vinyl playback mechanisms overall.