Found a lower profile way to seat my ROM replacement boards

I ran into almost the same thing fitting a Pico inside a 3D printed enclosure where the lid had maybe 3mm of clearance over the top of the board. I had soldered full-length header pins on first and of course everything was too tall, so I desoldered them with a soldering iron and some desoldering braid and started over. What worked for me was soldering the Pico directly to the carrier board with short offcuts of machine pin headers, same idea you describe. I pushed the pins into a spare breadboard first to hold them square, dropped the Pico on top, and soldered them that way. The breadboard trick kept everything vertical without me having to hold two things and an iron at once. One thing I'd add from my own fumbling: flush cutters on the underside after soldering. Even the short stubs poked through enough to catch on my case ribs, and trimming them flush underneath bought me another couple of millimetres I didn't think I had. I also tried thehardest way first, stacking a socket on top of a header, and it was wobbly and twice the height. Direct solder with the short stubs has been rock solid for months now, and if I ever need to pull the Pico out, the machine pin sockets fit over the stubs from the top.

On my Pico datalogger build the height fight got solved sideways rather than shorter. The plastic project case I used only left about 6mm over the board, and even short stubs were going to poke the lid. So I put right angle headers on the Pico and laid the whole thing flat on the base, with the wires coming off the edge instead of the top. Had to file a small notch in the case wall for the cable bundle, but the lid now closes flush.

Soldering the angled strips is easier than keeping round pins upright as well. I rest the strip on its pads, solder one end pin, check it sits flat, then run the rest of the row in a single pass with a wide tip. If it comes out crooked you just reheat and nudge it level. The catch is losing the option to pull the board out and swap it. When I fed 12V into the wrong pin and killed a Pico, getting it off meant melting every joint and lifting the board free with tweezers. Took most of an evening. The replacement went on the same way and has been running fine since winter.

Did almost the same thing last winter converting an old ISA card over to a Pi driver board, and the bit that saved my sanity was keeping the plastic spacer off the strip and snapping it back over the pins after I'd soldered them in. It acted like a jig and held all the round pins dead square while the joints cooled, no wobble at all. Also found letting the iron sit that extra second on each stub made the joints look proper instead of cold and lumpy.

I did the same thing on a Pico carrier where the case was tight over the USB end. What saved me was tinning each pad on the board first, then holding the stub with tweezers, touching it to the pad and letting the joint pull it in. No jig needed and they stayed square. Only burned my fingers once doing it that way, which I'm counting as a win.

This is helpful beacuse I've got a similar tightness problem with my own little project and I didn't even know those round pin strips were a thing you could buy on thier own. I always thought the pins and the plastic bit came as one piece you couldn't take apart. What do I actually search for to find the round ones, because when I look for pin strips all I get is the chunky square kind?

Update: tried the tinning trick, tinned the pads first and held each stub with tweezers and it made a huge difference, pins stayed square without any jig. Still fighting the joints though, a couple came out cold and dull and one wobbles if I press it. Is it worth reflowing those or just redo the pin completly?