Trim Tabs vs. Interceptors

Do you mean that you tried the same boat with tabs and interceptors, and experienced a meaningful performance improvement with the latter?
And if yes, what type of performance are you referring to, exactly: max speed, faster transition to plane, or anything else?
I am asking because it's somewhat rare to hear from someone who tried both systems on the very same boat.

We used to have trimtabs on our smaller Aquamatic boats up to 40 feet and since several of them are with stepped hulls, I didn´t think interceptors would work because of the air bubbles created behind the steps. But we tried and it worked very well, so now we have Zipwake fitted to all of them. It is not so much for getting on plane, but to keep the boat from leaning towards the wind or when people move around. They are more effective and react faster than the traditional tabs. Our bigger models up to 80 foot have Humphree and since they are IPS boats the interceptors are mainly for trim.

Can you possibly confirm what size did you use, for both the 54 and the 80?
The stroke as I understand is 2" regardless of the blade width.

I'd be interested to hear also about their effectiveness through the speed range, particularly since you are talking of boats usable at either low(ish) or pretty fast cruising speeds.

Not necessarily.
I mean, it is always true that the need for stern lift is inversely proportional to speed, of course.
And I fully accept that many boats behave as you describe.

But some builders prefer to tune boats in such way that a touch of tabs is necessary also when running at WOT.
The rationale is that whenever sea conditions suggest to ride with the bow higher than usual (even if at the expense of optimal efficiency/engines load), you can only do that if the "usual" conditions require a bit of tabs, and by lifting them further you can increase the AoA.

I don´t have the size figures available, but in the 54/60 they are fitted and filling the end of shallow tunnels where also the prop wash is channelled. Both the 54 and 80 hulls are designed for IPS with a slightly lifting trim so the interceptors can trim down the bow. Since both have long water lines and pretty sharp entries, they actually run smoother with the bow trimmed down also at high speeds. These boats also have Seakeepers to keep them stable in lower speeds.

Do you mean that the blade shape is rounded to follow the upper profile of the tunnels?
I've seen Humphree's interceptors with a blade profile that follows the lifting rails, but never a rounded one meant to follow prop tunnels.
I tried to google for some 54/60 stern photo on the hard, but couldn't find any.
Do you possibly have one (or a drawing) that you don't mind publishing?

Fair enough.
I misunderstood your statement as a generalization, based on what happened with some specific boats.

The IPS are fitted on flat tunnels...

Very interesting, thanks.