I guess you mean this ("positioner heart surgery"):
Digipower SG2100 DMSI SUPPORT
PS. A somewhat sharper version of the schematic of the sg2100 is here:
SG2100 Woes
If you can read the schematic, and don't want to exceed the regular 18 Volts, another option comes to mind, I would say.
Not inserting the external power at the plus-voltage-relais-contacts (needing 3 cuts, and two extra jumper cables), as in the link above,
but inserting the external power already at the V+ (needing just one cut, and no extra jumper cables, if I 'read' the circuit board correctly).
In that case, the collector/emitter ports of Q1 and Q2, and the relay coils (plus extinction diodes), also use the external power. No problem, though, I would think, if at least the external power supply doesn't insert RF signal as well.
Greetz,
A33