I’ve used it a lot, its also known and marketed as Alum-A-Lead. It spreads like normal bondo but it adheres stronger but doesn’t work well for really thin coats like putty does. it has a bit thicker consistency because of the aluminum particles found within. it also takes longer to dry. if you do order it make sure to get extra hardener because i feel that its harder to judge because the color (grey) doesn’t change when you add it and its a liquid hardener vs a cream
I have used it and here is my opinion. Way too hard to sand and still brittle if flexed. Nothing in the filler market can approach a leaded seam done correctly but if the stuff makes you feel "better" and you don't mind the extra work sanding it sticks and lasts as well as the rest. I like evercoat filler as it sand to dust, doesn't clog and sticks and feathers great.
Bottom line on a sail panel area, if there is flex a filler will crack.