Spanx Higher Power Briefs - yay or nay?

[Puffinity]

I am getting married in a few weeks and think I'd feel more confident if I could cinch everything in a bit, so I'm considering getting these [https://www.amazon.co.uk/Spanx-Higher-Power-Brief-Skin/dp/B003F5K2V4/ref=sr_1_1?ie=UTF8&qid=1464538377&sr=8-1&keywords=spanx+higher+power+brief magic knickers]]. Just wondering if anyone has any experience of these. Specifically, are they true to size? (I'm a 16-18) Do they do anything for your waistline? Do they stay up? Are they comfortable enough to wear for 10 or so hours? Can you get them on on your own (I'm think loo breaks!)?

Your insights are much appreciated!

magic knickers working link

Spanx higher power are great but I personally prefer the version which are like shorts at the bottom as well - they're much comfier as you don't have the compression ending around your hips. They do help the waistline but they really smooth everything out.

these ones

I can get away with a size down ..... But I also prefer the wear-your-own-bra body rather than shorts, always feel there's a "join" at the top of the shorts! But wedding dress styles often preclude straps ....

I just got a pair, I like them, they hold me in the same as the cheaper JL ones but they are a lighter fabric. The shorts roll up on me. Size wise I was on a cut off point so went for the bigger size as advised.