When I posted this thread, I had no intention to post an answer, especially the first answer, but here I go.
The LRB forging is not the same quality of Mahle, but okay. It is advertised to not be made in China or Taiwan. It was reported to me that he has the machine work done I'm Europe.
I know Europe is a big place, but the country of manufacture was not revealed.
For all wrench heads, machinists, and former machinists, the slightly out of square directional arrow raises the eyebrows immediately, right? Off by about 5°. But that doesn't tell the whole story.
The machine work on the LRB piston I used was quite good.
The windows were a bit smaller than oem Mahle , but were easily enlarged with a burr and rotary tool without harming structural integrity..
The donor saw was nib.
I didn't have scales, but the pup seemed perhaps a few grams lighter than the new Mahle I removed.
The pup raised center is .025" while the crown and skirt both measured within .00001" or so of the Mahle piston. So back to machine quality i was quite impressed to see tolerances that close and consistent.
Consequently, the Mahle and LRB pistons both measured real close to .003" clearance at the skirt/bore. I don't recall the crown exactly but i believe it was about .006".
WP CL to piston top on pup was .0025" less than oem Mahle.
I didn't get a real good measurement on the strato pockets, however they were remarkably similar in size and location to the OEM Mahle piston.
The piston height on intake and exhaust sides of pup was within .001" of the OEM Mahle piston.
By far the biggest difference between the LRB pup and OEM Mahle piston was the reduced distance from the ring land to the piston top of the pup. Let me say that differently. The ring land is higher on the pup than it is on the Mahle. Because I considered the difference inconsequential, I didn't measure it. But it's very obvious with the naked eye. A guess would be ring land is .020" nearer piston top on the LRB pup when compared to the Mahle OEM piston.
I should have, but did not take pics of either piston. Didn't give it a thought, but I believe I'm going to do this again soon with a another new saw/OEM piston and I can do it at that time.
Since I have no pics, it's my oppinion call. I believe overall the machine work on the LRB pup to be quite good. Not Mahle good, but again, quite good. From machine tool markings it appears the machine feeds and speeds were very similar between the two pistons.
Ring land clearance was nearly identical between the two pistons at a tight .002" measuring with a feeler gauge.
I installed the LRB pup on a new 2020 week 10 I think it is. So although the saw was new, it was still not the newest 562XP iteration.
Squish was set at .019" .
The oem gasket was .030" with a factory squish of about .026" near as I can remember. So with the oem piston installed, a full delete would not have been close to possible on this particular saw.
I opted out from the oem ring in favor of a Caber F cast.
Wrist pin was acceptably tight in pup.
Saw had about .005" bottom cylinder flange to crankcase clearance, so I removed .020" from the flange In order to have appropriate clearance.
I took a hint out of a video from Walt, the HTSS/afleetcommand owner/entrepreneur, and removed a bit more than .100" from the cylinder flange in front of the lowers and removed all casting lines and smoothed transfer divider edges.
I've had time to run 1/2 fuel load through the saw with a moderate to pretty well open modded muff, and 6° ignition timing advance.
High octane non ethanol with Turbo 108 booster because of the timing advance at a 40:1 mix ratio.
I didn't touch any cylinder ports. They remain 100% oem
I didn't check the psi, but it's good/high.
The saw probably will take awhile to seat the F cast ring.
At first I was easy on the throttle, but I did go wot for a few cuts after AT calibration.
24" 84dl Sugi and C-83 X cut. The saw handled the 24" quite well.
As a hobbyist, my oppinion is that the throttle response is quicker now with the pup, and the saw easily pulled the 24" b+c in a cured red oak round. Also seems to start easier.
Because the cylinder was only lowered about .010" - .012", it was not necessary to cut relief for transfer port caps retaining screws.
The muffler surprisingly was a bit snug for such a minute change so I enlarged the lower holes in the muffler with a drill and burr.
I thank Walt of HTSS/ afleetcommand fame for his great 562XP videos and advice. They were very helpful to me.
It's only my oppinion as a hobbyist, but for about $60 for a pup in a box and a piston ring, it seems to be a good power ( feels like more torque ) gain. I don't know if this is good for commercial work. I will leave that decision for those with a higher pay grade, but from what I've seen, not yet experienced, I wouldn't be afraid to try it.
When I started this thread I hoped to hear from someone else that already used the Little Red Barn 562XP pop up piston. Maybe from one of the pros on this forum. Since i received no posts, I went for myself.
This thread is relatively new, so if there is anyone that has done this, please chime in. Inform this hobbyist and others about your experience and knowledge. I would appreciate it.
I'm not attempting to promote LRB pup for the 562,XP. It's just that the 562 XP is one of my favorite saws, and LRB is the only manufacturer of a pop up piston for this saw to my knowledge.