Mounting Triplanar Tonearm to SME 20/2 Turntable

@millercarbon I can drill two holes and might just do that.  The third hole is not possible since it's in open space.  
I could also have a wooden disk cut to the same size circle as the SME arm board and attach the TP arm to it.  I don't want to detract from the aesthetics of the system, but I suppose I can paint it  black so it blends OK.  
One other thing is I live in St. Paul, which is where Tri-Planar HQ is located.  I've contacted Tri-Mai and he said he can help me set it up.  I would still like to hear other ideas on how to best convert this before I meet with him.  Thanks for your help!

@atmasphere Thanks for your advice, Ralph.  I appreciate it because I know you own a Tri-Planar and it was your recommendation on these forums that I began researching them.
For the record, the plinth of the SME deck is not the same material as the arm board.  The arm board looks like machined aluminum.  The plinth is something else, I'm not sure the material.  
I'm considering making the existing arm board work, but haven't decided yet how.  Tri Mai says he can help me figure this out if I want to go this route.
I've also contacted SME about ordering a blank arm board from them.  I'm assuming the price for this will be more than I want to pay.  They charge $9 for one of their own hex wrenches (standard metric sizes), as an example of how over priced their accessories are.  One can only assume the arm board will be hundreds of dollars.  That said, if going this route is the best way I will spend the money.  
@imhififan Thanks for the link to the etsy listing.  That would likely work just fine and be very affordable.  
@millercarbon Thanks for the suggestions.  Much appreciated.  I like the idea to experiment with different materials.  

A friend of mine owns a machine shop and has agreed to make one for me.  BTW, I think the material for the SME original is brass.  I took it off the plinth and noticed it feels much heavier than what aluminum would weigh.  
I'm going to see if I can get the new one made from brass as well.  
Also, a guy in the U.K. offered to make a custom board for 670 UK Pounds.  I think that's more than $800!  Crazy.

I made a temporary arm board last night from aluminum disk material I found online, and mounted the new tonearm.  It's not real pretty but it works great.  It only cost me about $30 for the materials.  At least I can listen to records while a nicer version is being machined locally.  

The Tri-Planar arm is an amazing work of engineering.  I'm already blown away by it.  I've only played one record and still need to tweak some things, but it's immediately evident that it's a wonderful tracking tonearm.  

Today my machinist friend confirmed that the SME arm board material is brass.  He's going to make the blank version for me out of brass as well.  I'm surprised to hear the plinth is aluminum.  It's such a heavy turntable, and besides that I would think aluminum would not isolate vibration as well as some combination of materials.  If it is aluminum they did a great job making the thing rock solid.  Thanks