...for future reference for others I'd be curious to know what others may have done differently to troubleshoot...as we all want to learn from others experiences and maybe help someone out in the future who reads this thread.
Let's start by recognizing a cold hard fact:
everyone who works on airplanes, cars, motorcycles and boats
regularly gets a new lesson...usually something not previously seen or considered in their personal experience.
I've seen this one (intermittent, momentary power loss which could not be duplicated on the ground) twice. The first time was a friend's Kitfox. The 582 Rotax had sagged a few times. Much looking did not find a specific cause, and then the problem seemed to disappear. When it came back it was at exactly the wrong place, on takeoff from a short strip. The result was a controlled sink at minimum speed into a forest. My friend did it right, using the 32 knot stall to maximum advantage, and he walked away unharmed.
Postmortem, engine on a bench: it was a tiny piece of plastic flake, perhaps 1/8" diameter and 0.010" thick, which had made it to the fuel entry of one carb. It was apparently swirling around in the bore
above the float bowl needle valve, and when the planets aligned just right it could settle on the needle valve passage and block fuel flow. A 582 running on one cylinder will not keep a Kitfox aloft.
I was one of the airport guys who helped look for that sag, and supposedly the most experienced. I felt responsible.
That was my lesson.
Fast forward more than a few years...the RV-1 (rightfully) scares **** out of CB with a momentary power sag on departure, 300 feet up and heading out over the trees. You've read the rest of the account. I did all the usual things, including a visual tank inspection, fuel flow measurements, line kink checks, inlet screen, gascolator, uphill ground runups, ad nauseum. Didn't find a single smoking gun, and I was uncomfortable. My
learned response was to talk it over with somebody, and in this case the best bet (for a bunch of reasons) was Walt. The process of describing a problem and what you've done, the back and forth of fault proposal and logic review, and the simple act of comparing experiences may be the best way of ferreting out a solution. In this case, almost as an afterthought, Walt said "Hey, it's a long shot, but maybe you should check...", and that was
it.
So, in answer to your question, I'd say talk it over with somebody. Somebody as experienced as Walt is a great choice, because he has been around long enough to have gotten more
lessons. However, I don't think it has to be someone with more experience. It just needs to be somebody with a set of lessons
different from yours.
BTW, right now both you and your mechanics are kicking yourselves about slosh in tanks.
It will never happen to any of you again. You've all got the slosh lesson in the bank.