I am also dual rated (A109/S76 and Boeing Captain)and the only way I can do this is by having more than one employer.
Things get interesting when I get close to flight time limitations i.e I have to say no on occasions.
However I do get 2 salaries, albeit one of which is a part time salary.
IMHO you have 2 licences, and whilst you cannot be in 2 places at once, you should still be rewarded for the flexibilty and skills you offer.
I would suggest that 1.5 times the higher of either a Bizjet or Helicopter Captain's salary would be fair.
By the way, if there is anyone out there looking to recruit...............
