@thompjs - since the B2 record is 2 @ -39 and there are no restrictions on use of the light line in that division it would probably be prudent to go to -41 in order to be equitable to all B2 skiers and account for inevitable progress. The other way to go that would be in compliance with 8.04© would be for the Technical Committee to only approve a single piece 21.5m line and a 1.5m handle section - e.g. no take off loops.
Rule 8.04© [as I'm positive you know from experience] reads as follows:
The tow lines must be made in two sections consisting of a single line 21.5 meters long (70' 6.5") and a handle section 1.5 meters long (4'11"). Twopiece lines must be provided by the Tournament Committee, and the 21.5- meter section, which can be attached to the contestant's handle section by looping the lines together, must be made available. In addition, colored multisection lines may be used if the Technical Committee has specifically approved their design and type.
Looks like the its been thrown over to the Technical Committee to decide.