I'm in the US so I'm thinking underworks would be the cheapest and fastest way to get a binder and they're highly reliably from what I hear, but I don't know what one to get.

I'm severely overweight, so my measurements according to underworks' site's directions I get a 47.5 average (I wear a 44DD bra). I weigh about 260 lbs and am 5-foot-4 with a long torso and shorter legs. I am considering the 988 (the one with chest only compression) or the 997 (the double front).

The thing I am worried about is breathing. I am also worried about the 997 being so long that even when I tuck it into my pants it may roll up.  But I really want the compression of the 997.

A have a couple questions:
For bigger guys: do you have issues with the 997 rolling up? If yes, to what extent? And if any of you have the 988 (i don't hear that mentioned too often) and have a large chest, is the compression long enough to cover your chest?
For the general population of transguys: Do you think the 997 is worth the constrictions on breathing?

I'm a smaller guy (I actually wear an XS, though my measurements put me in a M) but I'm a soft squishy smaller guy who has some problems similar to the big guys'. In general, I find the 988 immensely preferable to the 997 - the compression is actually better (I think it has a double layer on the back) and I like being able to breathe. And it doesn't roll up.

The one problem is that because I'm soft and squishy, and because unlike a sports bra there's no band at the bottom of the 988's compressed area, my chest tends to slide slowly out of the compression area if I'm very active or wear it for a long time. It's not terribly noticeable on me but it's visible if the front of my shirt pulls taut (but then, so are a lot of the problems I have with other binding methods, like the line formed by the Frog Bra or the weird chest shape with the 997).

I wouldn't get another 997 for the extra compression (there isn't any). I might get it if I actively wanted compression on my belly/hips, but I'm not sure it really looks any better with clothes on. If I were concerned about the length of the compression area on the 998, I'd probably get a Tri-Top. (A DIY option is to get a Tri-Top and one of their extra-light-compression cotton tanks and sew them together to make your own version of the 988 but with a longer compression area)

I'm not built the same as you, but I've been wearing the tri-top for the past few months. It seems to get the best reviews across body types, and you can avoid a lot of the riding up issues with it. I fold the excess of the tri-top back on itself and it works great.

One other thing you might want to think about: not all binders are sized the same, even from the same company. My measurements placed me squarely in the middle of Medium for the tri-top, but I would have been somewhere on the edge for some of the other binders. I don't like having to choose between too tight and too loose. Too loose is obviously bad - not flattening enough.

Too tight also worried me. Beyond the medical risks associated with binding too much/too tight, I was afraid I just wouldn't be able to get it on if it was too small! As it is, the first week or so of putting on the RIGHT size took some effort and figuring out. I know people have tricks (step into it! over the head! underarmour underneath), but in my case, I have physical and anatomical reasons that I struggle to put on and take off even tighter tank tops, let alone a binder.

Bottom line: I recommend the tri-top so long as your measurements do not place you between sizes. If they do, then I'd get another binder where your measurements are more clear about proper size.

So there's no band at the bottom of the compression on the 988. That eliminates that. I had no idea that there was no band. I automatically assumed it did. My moobs are quite saggy, despite my young age and lack of binding until now; they're mostly fat.

I hadn't thought about the tri-top. I saw someone mention that it rolls up on large guys. I don't know if that's true for all large guys though.

I'm thinking I'll order the 997, for the slimming effects, and since it's the same price as the tri-top I could always exchange it. I hear underworks has a good exchange/return policy.

I plan on wearing a sports bra underneath it to prevent chaffing and to hold things in place. Is that a good idea? I hear some of you guys say that you do that.

I don't wear a sports bra under mine - I find that just combines the discomfort of the sports bra (the band around my chest) with the discomfort of the binder, and doesn't really seem to add anything. And it makes the armpit bulges worse. Other guys' results vary.

I'm not a big guy and the bottom part of the tri-top rolls up on me a little. Seems pretty common and no big deal.

Otherwise, I don't wear a sports bra underneath. At first, I wore an underarmour heat gear t shirt underneath, which is a little bit compression-y AND makes getting the binder on and off without chafing easier. I think that's a better route than a sports bra, which may just give added bulk.