I want to expand on Doug's point 2a, which is the reason why I require Galibier purchasers to send their Tri-Planars to me in order to drill their armboard.
The Tri-Planar (like the Schroeder Reference), has an arm mount that is concentric with the VTA tower. The VTA tower is offset from the arm's bearing pivot point, so any fine rotation of the arm's mounting orientation (the three holes) will change the pivot to spindle distance.
With Galibiers (unlike fixed mount turntables) getting the correct pivot to spindle distance isn't a problem because one can rotate the armboard to bring it back into spec. I do however want too ensure, is that the Tri-Planar is nicely oriented when it is parked in its armrest, and if I rotate my armboards to bring the pivot to spindle into spec, there's a possibility of making the mount look a bit "ungainly". I like the arm to point front to back, which is not only aesthetic, but also provides a reasonable amount of clearance between the headshell and the platter.
Doug's bet on 2b (bad mounting jig) is one possibility. There is another more probable one. In the end, it doesn't matter because the solution is the same.
When a Tri-Planar is assembled, a large straight-slotted screw on the under side of the VTA tower is torqued to spec . There's a remote possibility of a couple of degrees of slippage (rotation of the mounting flange) when this screw is torqued to its final specification. This would lead you to believe that the jig is wrong.
Any jig made for a Tri-Planar presumes that the mounting flange is oriented perfectly, and I would NOT bet on this.
I think a more accurate statement about the mounting jig is that they are not consistent with the rotational orientation of 100% of the Tri-Planars in the field. There may have been several generational drawings of this jig based on different samples of Tri-Planars (mounting flange orientation), and you could call any of them right ... or wrong.
My point is that even the metal jig should not be trusted, because of sample to sample variance in the mounting flange's orientation. Don't waste your money on the metal jig. You are still advised to follow the procedure I lay out below, using any jig as a STARTING point only.
Whether you have a "bad" jig or a mounting flange that is at variance with the jig can be argued about until the cows come home, but the solution is the same - forget about the jig and use your trusty ruler. I created my own Galibier specific mounting jig before understanding this idiosyncrasy, and my mounting technique is identical to how I'd mount the arm with using the supplied jig:
This is an imperfect world, and even Doug's and my tonearm of choice has its quirks. Doug and I make an effort to work you through the Tri-Planar's these idiosyncrasies. As an aside, I maintain a quite a few information pages on the Tri-Planar section of my website. Periodically, I try to link to Doug's generous contributions to this forum as well.
Given that you shouldn't mess with the bolt under the VTA tower, the solution is indeed a re-mount. On this, we all agree.
1. Mark all three holes using the jig, but DON'T drill anything.
2. Locate the arm over the three holes you've marked and observe: (a) the pivot to spindle distance (should be 233.5mm) and (b) how the arm is oriented when locked in the arm rest (you should like how it's oriented and ensure that it clears any dust covers, etc.). Note - you may need a third hand (either human or a soft jawed clamp of some sort) in order to hold the arm in place while measuring.
3. Once you've arrived at a nice position for the arm, center punch, drill (and tap as necessary) ONE hole - the one on the left (closest to the platter).
4. Mount the arm by this one hole, and perform fine measurements, rotating the arm around this one point in order to achieve the 233.5mm pivot to spindle distance.
5. Mark the remaining two holes
6. Remove the arm, center punch, drill (and tap if necessary), the remaining two holes
7. Mount the arm
8. Use the slight bit of intentional play in the mounting holes to bring the pivot to spindle distance to a perfect 233.5mm
Note - if you're using an arc-style alignment protractor, then wait for your cartridge alignment step to perform step #8.
Cheers,
Thom @ Galibier