Dual Gasser Throttle Systems

[dragonz]

I currently have a couple of project bikes underway.
the first is a total rebuild og my 660, which is being built into a 719, & I will start a seperate thread on that (have lots of photos etc)
& the other is putting an RG500 (4cyl 2 stroke) into a YFZ chassis. (will probably do a seperate write-up on that too, time permitting)

My query in this thread however concerns the Dual Gasser Throttle setups available.

I ride Twist Throttle, tried the thumb for 3-4 years, always struggled with it, ditched it for the twist & after getting a few setup issues sorted, never looked back!
(Recently rode a friends YFZ & hated the thumb with a passion)

However the friends who I'm working on the RG project bike with all ride Thumb Throttle.

So,
I want to get a couple od Dual Gasser throttles so we can all switch between bikes & still enjoy the ride.
This is where it becomes tricky.
A major part of the setup that I had to get right was the tension of the throttle return spring to suit the twist throttle.
Quads are setup for Thumb Throttle, & as such have very light return springing on the carbs. The conversion to Twist required me to make a heavier spring for my carbs to suit.

Does any of the commercially available Dual Gasser Systems have seperate spring tension adjustment for the twist & thumb portions?

Thanks

Dragtonz