[Fr. Frank]

First of all, Doelfins will work on sterndrives, just as they do on outboards. They only create an appreciable drag when the drives are trimmed all the way down.

Second, in a chop, they are very good at keeping the bow down cutting into the chop for a smoother ride, and they cost less than trim tabs.

However, unlike trim tabs, they cannot be used independantly of the drive angle. This means that underway and planing, you cannot adjust the boat's attitude while maintaining the best thrust angle on your outdrives. Remember that the best outdrive thrust angle while underway on a plane is as close as possible to parallel to your direction of travel, given the detractions of ride quality and trim angle. For thhis purpose, trim tabs are much better.

Given cost considerations, I'd probably go with the Doelfin or Stingray hyrdofoil stabilizers. You WILL get on plane faster, and be able to plane at a slower speed.

I have a Merc 150 OB on a Seafari 20, and I have a Stingray XPRIII mounted to my cavitation plate, AND a stabilizer mounted to my skeg.
I plane in under 3 seconds, and have a top speed of nearly 50mph. It looks funky, but works well.