[Soundguy]

You could use a DA and plumb it that way.. perhaps a valve with detents.. however.. there are special concerns for using motors so that you don't cause shock loads when you center the spool.

You may also want to add in a 'clutch'.. IE.. a valve to sump that bypasses the spool so that you can leave the engine idled up if you need it.. etc.

I've not seen and DA spools that were friction loaded to leave them variably open.. though I'm sure you could rig up some linkage to the valve using perhaps a marine throttle setup..

soundguy