Mounting Triplanar Tonearm to SME 20/2 Turntable

Three choices. #1 buy a new tonearm board.
#2 laminate 1/2" MDF to the current tonearm board to cover the hole. Spray paint it black and make sure you can lower the new arm enough to get it down to platter level. 
#3 Make a new tonearm board. Layer plastic and aluminum layers to get the right thickness using slow set epoxy. Use the old board as a temple to router the board to exactly the same shape. 
If you don't have the stuff to make your own just buy a new one. 

Right???

@millercarbon  I do talk with the voice of authority fairly often, which probably isn't the best way to present things. But I try to temper that with simply not responding if I have any doubts. FWIW dept.: I own two Triplanars and Triplanar is a 10 minute drive from here. We also make a turntable - the model 208. I've serviced turntables of all types as I put myself through engineering school repairing consumer electronics. So I was expressing the mechanical engineering issues that are common to all turntables.


This issue is not unlike the steering in a car. The car has to keep the wheels on the road at all times, and at the same time you have to be able to steer it. To do this, there can't be any play or flex in any of the steering or suspension components or else the handling can get creepy really fast. In a turntable, there can't be any play between the surface of the platter and the locus in which the cartridge is held. If there is, the stylus will be able to move in a way other than the grooves of the LP dictate (introducing chatter and/or coloration). To this end there can't be slop in the bearings nor flex in the plinth. The arm has to be rigidly coupled to the platter bearing - as rigidly and also as 'dead' as possible (the latter being why damping a plinth affects the sound).  Otherwise that would be much like a flexible part in the steering of the car- and would result in the wheels not doing what you want.

I mounted a Triplanar on a SME 10, you @snackeyp might of bought the arm from me? Any how I had an armboard made of Delrin by Brian at Analogue Artisan and worked great he is in New Hampshire and does very good work. If you look at my profile I put some photos of it there. I found it difficult to work with Triplanar as far as getting an arm board   http://www.analogueartisan.com/

As others have suggested make a new armboard  a local machine shop should be able to help you.  Tri’s setup jig is a little “rough” when I mount Triplanar arms I use my DR Feikert jig on the tonearm directly then mark the hole locations on the blank armboard.

Are you selling the 4.5 ? If the price is right I’m interested 

Best of luck

Peter 

Happy Triplaner owner here also, I would suggest the visit with Tri to get you up and running and also establish a relationship- wish I was that close to him! He has always treated me well and I bought my arm used here on the Gon. 
On the subject of a third hole, not many two legged stools on the planet, but you can certainly try... 

as far as experimenting with other materials, Why not ? You may pick up some more critical listening / evaluation skills to boot. 
Enjoy your arm, I love mine ( on a Brinkmann Bardo w Lyra - she sings happy