I've tested and made overboard poles
Some years ago I made overboard poles for boats in our yacht club. We took large fishing pole blanks, poured BB shot into them and sealed the bottom. In flat waters they worked well but in waves, when they leaned over, the BB shot would run to the tip. So we re-did them by putting a plug in the blank and re-sealing them after the shot. They worked OKTesting them against other commercial top poles, they stood up almost as well. But even good ones (Forespar appears to make the best ones) were hard to see in bad weather which is when you would probably use them.Ones with lights on the top are much better to see. I haven't tested the new MOM8 inflateables; they are expensive.More to the point, the problem you are trying to solve is finding someone who has fallen overboard. Today I would recommend hitting your MOB button on your GPS. It would also calculate for drift. Everyone ought to wear at night a strob which is much easier to see. By the way, it is very hard to see a pole and flag even if it is white at night.After being out in fifty-five ktn winds and 8 to 10 foot swells, I think a pole is useless. I want my crew to have SOSuspenders (or equal), strob lights, and loud whistles. If I were rich, all would have hand held water proof VHF radios. The MOB can see the ship easier than you can see the MOB.By the way, you can get pole holders that clamp on your stern rail from West Marine and Defender. I suspect other boating sources have them as well.Good Luck.