Half/Twin Ropes

I just bought a new set of ropes that are rated as both Twin and Half.

Do I have to stick to one rating as I climb or can I clip them separately when I need to and together when the route and protections straighten?

The are the new Petzl Salsa 8.2mm

Thanks!

You can clip those separately if you want, I have the previous style of Petzl 8.2 ice floss and I'll even use off them by itself for alpine routes routes that might only have a couple of slightly difficult sections you'll want to be roped up for. I don't think that Petzl would recommend that usage per se, but either of your ropes will hold a fall on it's own, you're more at risk of slicing the rope on an edge if you just use one.

That's not what s/he's asking. The op is asking whether he can swap from twin technique to half-rope technique or vica versa on the same pitch. Old/conventional answer to this has been that it is not ok. I think it is more accepted nowadays. Bearbreeder had an email from a rope manufacturer that indicated that they thought it was fine. There is also a post from RGold somewhere on MP.com that gave some very well thought out pros and cons. Search for that thread, there were pages of debate. Personally, I'd be ok with it.

I believe it sort of eliminates the benefits of double ropes. It also increases anchor load. The benefit of half (double ropes) is less rope out per clip since you tend to alternate on straighter routes, and also much lower force on your gear. You might be able to alternate method, but it seems like there is limited reason to do so.