Did anyone actually make the stock 16-ft lineset work, or am I stuck buying more copper?

I made the stock line set work on my last install, but only because I moved the condenser instead of fighting the routing. My first sketch had a similar up-and-over path and by the time I laid the actual lines out I was over the length too. What saved it was realizing the condenser didn't need to sit exactly where I'd drawn it. Sliding it along the wall toward the indoor unit buys you length from both ends of the run at once, which adds up fast. Three feet of wiggle room sounds like plenty. Check the manual for the minimum clearance in front of the service panel and around the coils, keep it off the hose bib, and don't block where you'd need to stand for maintanence. A slightly snugger install beats a mid-line splice every day of the week in my book.

As for joining more copper, yes, there's a much simpler way than brazing. Line sets are sold with flare nuts alredy on both ends, and you can get flare unions, basially a short fitting with female flare connections on each side, and screw two lengths togehter with two wrenches. No fire, no special skill. That's exactly how the extension kits work, and some come pre-charged so you're not losing refrigerant in the connection.

The catch is that every extra flare is one more spot a leak can hide, and factory flares only stay good if you don't kink or re-bend the lines getting them up and over. If you go that route, snug the nuts by hand, then torque them properly with a backup wrench so you're not twisting the tubing, and leak check everything before opening the valves.

Honestly though, with 19 feet of measured run and only 16 feet of line, you'd be splicing right in the middle of the route, probaly up on that over-the-wall section where a future leak would be miserable to get at. I'd slide the condenser the three feet, reroute so the drop is shorter, and keep the whole thing on factory connections.

I'd push back on the part about pre-charged extension kits saving you refrigerant. The one I bought for a garage unit years ago wasn't anywhere near right for my run length, and the charge ended up off til an HVAC guy recovered and weighed in the correct amount anyway. A factory flare union holding two lengths together also sits there as a slow leaker on more installs than people admit, mine wept after two summers. If the slack exists to just move the condenser and keep everything factory, that's the route I'd take. Cheating toward the hose bib sounds ugly but leaks are uglier.

One thing that tripped me up on my first install, the line set comes coiled in the box and measures longer once you straighten it out. Mine gained over a foot from the coil alone. Also remember the factory lines include whatever slack you leave for the service loop at the condenser and the drip loop before it enters the wall, so don't plan on using every last inch. When I re-measured mine laid out flat on the driveway instead of eyeballing the path, the math looked a lot friendlier than my first string estimate did.

Agree with the guy who said the coiled line measures longer once it's out of the box. I almost ordered an extension on mine for the same reason, then uncoiled the set flat on the driveway and it picked up close to that much. Also seconding sliding the condenser over. On mine I angled the unit a bit on the pad instead of squaring it to the wall, and that alone ate up most of my shortage without looking wierd from the street. Worth trying before you commit to a splice.

Kind of in the same boat here except my shortage came from routing the lines through the basement instead of outside the wall, which ate way more length than my sketch showed. I ended up using a flare union mid-run since cutting the whole thing apart wasn't an option, and it's held for two seasons now. I do hit it with soapy water every spring when I clean the filters, more out of nerves than anything. One thing I still don't fully understand, when you say torque them properly, is there an actual number in the manual for that, or is it just snug plus a quarter turn? The paperwork with mine was useless on that front.

Update: got it done with the stock lines after all. Laid the set flat out on the driveway like suggested and sure enough it came out way longer than my string measurement. Slid the condenser a bit toward the corner too, doesn't look as cramped as I feared. Ran fine on the factory charge, no splices needed.