Grrrrrr.. can I say it again.. Grrrrrr...
I dont consider myself an idiot but maybe I need to re-evaluate.. OVERHANG.. is killing me.. I bought the GEO-DISC over 20 years ago. It has worked within reason I guess but wanted to make sure that the setup was accurate. Having the LINN and ITTOK there isnt an easy way to identify/lineup the pivot point. The arms center is offset so.. I have printed several protractors from LINN sites and have researched how to implement but have left scratching my head. They dont lineup/match the GEO.. not even close. Once the overhang is adjusted where I "think" it should be (using the GEO-DISC) I try to line up the azimuth by using the GRID on the GEO.. The second validation is assured by measuring, with a very high quality pair of dial calipers ,from the back of the screws that are mounting the cartridge to the head shell to the apex of the slots that are machined in the head shell. The measurements between the two screws to the back of the slots are within .001. Close enough.. But the BLACKBIRD still has distortion on some of the cuts. I am very perplexed. I can purchase a protractor but not sure if it will get me any closer. I like the one that is being sold here but it's 700.00 a lot of money that could be for nothing. I am pretty sure that there is nothing in the equipment , i.e. arm , table, BB, phono that is causing this. The BB is VERY quiet..

So the burning question is , what is the best setup tools and methods that you use to SETUP the LINN with the ITTOK arm specifically.

Have you looked at VinylEngines arc protractors ? Big thing with them is to make very sure you printer doesn't scale them and create a error - they all have a scale built into them that makes this easy to check.They are free - great turntable/arm/cart site.
This is probably not an advice that you will like, but in your place I would find a dealer in the area who knows Linn really well and get him over to do that alignmet thing right. And I would observe him do it. Sometimes we just need a little of assistance.
The Geo-Disc is pretty useless for a significant percentage of tonearms out there ... including the Linn.

Linn's own protractor disc, as part of the Speedchecker, works very well for their arms -- allowing you to verify the alignment on both the null-point grid and the overhang arc, both optimized for your arm geometry. IIRC the pricing isn't too outrageous ... the complete Speedchecker isn't too much more than a high-end protractor like the Mint, and you get highly accurate speed calibration as well.

Another nice tool is Linn's Kinky, which fits in the arm collar and verifies the exact spindle-to-collar alignment. It can reveal such issues as the armboard out of alignment, or a bent subchassis. They're expensive, but a nice Linn dealer may let you borrow one.
I use a Mint LP protractor with my Sondek 12 and Ittock LV II. It is tonearm and turntable specific, but can be used with any LP 12 using a Linn arm. I am currently building a second Linn turntable, but can loan you mine when I am finished. Good luck.