"More likely to show" as an erection if it were DOWN?? How do you figure? What would be more obvious than a penis in the up position that then got erect?
Of course, in a Speedo, I suppose it's a moot point.
An erection is much more likely to "tent up" and protrude prominently, when the penis is in the down position. For it has nowhere to go, but to stick more straight out. As the penis grows longer, becoming somewhat erect, it can't bend as it's getting stiff also, so it tents up and even twitches or throbs, making it even more obvious that it's growing.
Isn't that why the other guy said he repositions his penis to the side, but then of course, as spontaneous erections will do when they find more room to grow, it "straightens up" more towards a full-on boner, and then shows more of a big long bulge?
I agree with repositioning, hopefully not-to-be-noticed, so that the stiffening penis or semi-erection doesn't either bind or tent up.
I remember when I used to go swimming, being very conscious of my penis trying to get aroused and hopefully not swell too noticeably, at seeing so many sexy women all around in skimpy bikinis, with such beautiful curvy breasts. I wore just regular swimming trunks, with penis in the down position, where the penis, if it gets too excited, would easily tent up. The typical inner liner, is way too comfortable and loose, to contain a stiffening penis in any but the down or "tenting up" position. I was never on any swim team, so no need to ever have a speedo. Besides, are speedos modest enough? Didn't bother me if other guys had speedos, but I never had a speedo, as why do I need to be "on display?" (Some boy at summer camp said I have a "big dick," but no reason many people should need to know.)
But I agree with all the different penis point directions, as penises do not all come in the same size, nor all lay in the same natural positions. Some guys say their penis fits better, pointed up, as their balls or something are too big. What does it matter that a penis in the up position, might almost reach the waste-band edge? Of course the guy isn't planning to get erect, and could reposition to the side where there's more room, if it started getting hard, before it "escapes." Some flaccid penises are too long to point up, and might go better to the side. Some guys are so large in penis size, that only down works for them. Whatever. I don't think there's any such thing as being "too big for a speedo," but rather, just a bit more challenge to find a proper fit with sufficient room. For we wouldn't dare say that a woman's breasts are just "too big?"