I don’t think the Triplanar can be fit to an existing SME mount as I had this mounting in my decks second position. Instead you’ll need to drill a new mount
Best to avoid drilling new holes in the SME if you can do as not to affect resale, Instead have a blank made up with countersunk holes to match the SME mount. Countersunk is important so that the bolts do not protrude above the sub plate top surface and foul the new arm. Then have the three threads for the Triplanar drilled in that. Use threads so you don’t need to bother with bolts below the surface of the new sub board. The only challenge you might have is with vertical clearance but as I’ve had an SME and a TP simultaneously mounted on my deck with this arrangement I believe it should work
Any competent machinist can make up a plate like this for you, try asking your local turntable dealer if there’s someone they use.
Best to avoid drilling new holes in the SME if you can do as not to affect resale, Instead have a blank made up with countersunk holes to match the SME mount. Countersunk is important so that the bolts do not protrude above the sub plate top surface and foul the new arm. Then have the three threads for the Triplanar drilled in that. Use threads so you don’t need to bother with bolts below the surface of the new sub board. The only challenge you might have is with vertical clearance but as I’ve had an SME and a TP simultaneously mounted on my deck with this arrangement I believe it should work
Any competent machinist can make up a plate like this for you, try asking your local turntable dealer if there’s someone they use.