On the saddle valve punching front, in another
thread Iffy pointed to a specific saddle valve available on e-bay that has apparently worked well (the one I tried from Ace Hardware didn't), runs just under $10 total including shipping. I've ordered one to test it out (I use a dremel, slotting, since I already had one).
This is the product I tried, on Ebay: RO DI REVERSE OSMOSIS SADDLE VALVE ADAPTER FILTER, $6.99 + $2.95 S&H. It consists of two blocks of machined aluminum (?), with a single large brass bolt used to provide the compression between them.
To use it, screw the piercing valve down until you see it protruding as far as you want it to penetrate, then count the number of turns to retract it back into the main section. Put the carto in place between the two parts of the saddle, and lock it in place with the brass fitting. Screw the piercing valve back down, N turns, then retract it.
For me, 2-1/2 full turns seemed about right. Very little carto deformation, a single small, clean, hole. The hole is small, so I'd put several of them in a carto, else widen the hole slightly with a regular nail or countersink/punch once the initial hole is there. Moderate fiddle factor, getting the carto in place, since the bottom half of the saddle is a separate piece of aluminum, however the net result is pretty nice. Much cleaner hole then I got with the saddle valve from Ace, it looks like the piercing part is nice and sharp.
I'll stick with my dremel, slotting, since I already have one and it is fast for me. On the other hand, at $10 (much less expensive than a dremel), this isn't bad as far as I can see. YMMV
