Hi all. I know I'm not the first or last person to ask these questions by far, but I'm planning a trip to WDW in February with my partner for the first time, possibly the only time (though I certainly hope not) and I just like having as much information as I can have going into things like this. I've already gathered a lot of information from several places on the web, and they have all been a tremendous help in planning. However there is still some information I'm missing so I'm just going to come out and ask.
We're both roughly the same size. I'm 5'11, 58" waist 56" hips, he's 5'10 with the same measurement. We've already decided on most of the rides we're going to be going on while we're there and I feel pretty good about us having no problems with them. Though on some, like Big Thunder and Splash mountain it looks like we have to ride separate rows, which is fine, it's just hard to tell from the pictures I've seen if that will be the case or not. But even if it is, no big deal.
In any case, though, there are four rides I have my concerns about. Space Mountain, Star Tours, Tower of Terror, and Test Track. As you can tell I picked three with seat belts and one with only 1-wide seating so you can see why I might be concerned. So I wanted to see if I could get some input and advice on those rides specifically. With Space Mountain it's mainly the width of the seat that concerns me. As for the other three, well of course, my concern is how long the seat belt is and how crushed we would be sitting next to each other.
Any advice would be appreciated. Thanks.
My girlfriend and I were actually roughly the same size as you when we went for the first time. I was about 60" waist at the time (I've lost 80lbs since then

) and though she is smaller, we're both really tall for women and have broad shoulders. Let's talk about those rides.
Space Mountain: It's a bit like sitting in a rowboat and trying to stand up. The ride itself is fine and the restraints are no problem! But you need to be able to lever yourself up and out of those seats, then out of the cars. As long as you have some upper body strength and no knee problems, you will be perfectly fine. It's just an awkward one to get up and out of!
Star Tours: The seats were a little tight at the time, but still easily gotten into. Think of it as a movie theater seat. I would personally avoid the back row. The best advice I have for this is to pull your seatbelts out first, sit, then buckle up - it's dark in there even with the lights on and it can be hard to find the seatbelt input if you're carrying some weight.
Tower of Terror: No problems here at all. There are seatbelts for each individual and the seats are a good size. Enjoy!
Test Track: Ask for the front row if you have longish legs, and for a row to yourselves. We sat (me 5'11, close to 400lbs at the time - my girlfriend 5'9, 320lbs - and my 5'7, 175lb mother) all in the same row and the only issue was foot space. Not enough for 3 tall people! Another suggestion here is to pull the seatbelt out and sit again. It's like a car belt, but can be tricky to wiggle around to grab if you're bumping into another person trying to do the same.
Splash and Big Thunder: As long as you and your partner don't mind getting cozy, you may be able to ride this together. My girlfriend and I did Big Thunder and sure we were smooshed, but we don't mind

I rode Splash with my mother, but honestly she is average sized so it might be a bit much for you guys, hard to tell. If you feel uncertain - ask the Castmember! They see it all and there was never any judgment when I asked if they thought we'd fit.