Chris cut out a cocobolo armboard for use of my SME Vd on a Teres 255 (lead loaded acrylic platter). When I upgraded to a Teres 320 I kept the same armboard. It is not a simplistic cutout and cocobolo is an extremely hard wood, so I'd definitely suggest having Teres make the armboard for you.
As you know, the SME IV and V do not have slotted headshells - instead the stylus' overhang geometry is set by a unique sliding base capable of very fine adjustment. On the sled the entire arm moves, including the underslung post containing the wire feed to the DIN connector. This means two things: i) because the arm's post and DIN receptacle hang partially below the underside of the armboard there must be enough wood cut out to allow the post to move freely, and ii) in the case of Teres armboards mounted directly on the plinth (such as with the 255 and current 2XX models) the backside of the SME's right angle DIN receptacle almost butts against the plinth when using a short lengthed cartridge such as a Shelter 901. That is, it comes within less than a hair of hitting the plinth when the arm is moved forward on the sled and thus comes that close to not allowing proper cartridge overhang. On even shorter cartridges such as a vdh Colibri, the only way to move the arm close enough inward is to cut a notch in the plinth itself to make room for the sliding DIN receptacle. (I hope that is clear - at least for SME owners.) If your cartridge is not short, none of this should be an issue.
In the case of the larger (no longer made) Teres turntables such as the 320, the armboard sits on a lead pellet filled pedestal that raises the DIN receptacle above the height of the plinth, which eliminates any clearance issues.
Having only heard Teres TTs with the SME V, I have no basis for comparison of sonics with Galibier. Mounted on the 320 the V allows my Transfiguration Orpheus to offer its musical virtue unhindered. Heh.
Since Teres appears to be moving away from large wood platters, and with that (at least for now) comes both a sonic and a price point void between the $4300 model 260 and the $14000 Certus, I would inquire about Chris' plans for an upward migration path, or otherwise filling the spots occupied by the 320/340/360 series. I doubt you can go wrong with either table and suggest taking a careful look at workmanship and materials quality along with customer service.
Tim