Maybe everyone else already knew this, but it was news to me.
Jim Aron had good results with the new 25LAs a few years ago, so I had waited for a Tower "deal" and got a pair of them for some ridiculous price (maybe $45, but so low it didn't register). They just sat since then. I don't know if this is a reliable indicator of the "new" VS "old" LA, but these came as bare metal as opposed to painted blue like those I had tried and seen other people use in the past.
Today, after flying "Stunt 25" with the Skyray/20FP at the Ted Goyet contest, I popped one of them on the airplane just to see how it worked. The answer is - very good. I decided to read the directions and follow them *to the letter* to see of there was anything to be learned. I bolted it on the airplane exactly as it came, plastic backplate, rear needle, everything. The needle was supposedly set at the factory to a good break-in position. I primed it as it said and it started on the first flip and ran at a *perfect* break-in setting well into the 4-cycle. After a tank of gas was run through it (which, I might add, didn't take all that long), I put on the flying prop - APC9-4, naturally - and did some testing. It peaked out at over 14,000 rpm right away, and had no problem holding a 4-stroke at maybe 12,800. This is *much* stronger than the 20FP I had been running and at least some stronger than a perfect 20FP. This is much different from the older LAs I had tried, it is *much much* more powerful.
We flew it and had the same issues we typically had with the 20FP - that is, the fuel consumption was astronomical, and the needle was changing rapidly. Maybe 4 minutes on 3 oz, set at 13000 at launch, and steadily richened up through the (brief) flight. Fired it up for the next flight, and with the same needle, it was down to maybe 11,200 and was dead rich. Tweaked it back to 13000, launched again, and it ran longer and richened up throughout the flight, but not as much. Firing it up again at the same needle got about 11,800, dead rich again. Went through a a few flights doing this and we got 11,200, 11,800, 12,200, 12,400, and 12,600, tweaking the needle more closed each time to get back to 13,000, and the duration of the flight on about 3 oz went longer every time. Eventually we could get through a complete pattern on ~2 oz, which held there the rest of the afternoon.
Otherwise, the in-flight performance was quite good. The air was a gentle wafting 15 mph breeze and we had a lot of time to fiddle with the Skyray since almost the entire field of the contest passed their second round flights. Flying my regular airplane, the air was not all that bad, and at no time was I concerned, but it was definitely a stiff breeze and certainly not something you could just ignore. The Skyray/25LA was very fast but had the "slow motion" feeling most of the time, and had no issue getting through the pattern. Occasionally it would briefly go rich in overheads which didn't add a lot of confidence, but the rest of the time it was very consistent in flight. When we tried backing it off into a 4-stroke in level flight, the power boost in the maneuvers was more than you would want. This was no surprise, this is not a Fox and that's about what happens with any of these engines (20/25FP. Brat 28, OS32, Magnum 32, etc) with the stock parts. Of course there was abundant opportunity for whip-up but it was no worse than any of the others in that respect.
One day and maybe 10-12 flights isn't enough to draw any conclusions but it seems like the engine has a lot more potential than the "old" LA that was clearly less powerful than the 20FP. It would certainly spin more prop than a 9-4 APC and would clearly fly A LOT more than a 400-square inch 29 oz airplane.
By the way, the rear needle and plastic backplate seemed to work just fine. Once the engine settled in, the needle settings were dead-nuts repeatable, predictable, showed absolutely no problems. One click was a pretty big change, which is about my only possible criticism. It looks like the needle would be very prone to breaking off in an inverted crash, which is no better than the conventional needle, but I would be a little concerned that the needle assy. hitting the ground might crack the part of the backplate you care about. Another feature of my particular installation was that the plumbing ran all over the place, since I just took off the 20FP with a conventional spraybar and hooked up the rear needle with the same tubing, etc leaving a big loop, and the filter hanging out near the cylinder head. This led to some starting issues since it was very prone to the fuel running out of the lines. We use the same technique as with it's big brother 40VF - flip through with finger partially covering the venturi and removing it quickly once the engine fired up to prevent flooding it off. I don't dispute those who have had a problem with the backplate leaking and maybe mine will too, at some point, but so far it seems to work with no issues
Brett