I think it depends on what mics you plan on using. Schoeps MK and Neumann KK pairs will work. A Sennheiser MKH40/30 rig won't fit in a mono Rycote all that well.

While it is not ideal, it is possible to fit an MS pair inside a mono Rycote. Especially if you can find the older, non-lyre based blimps. You just need smaller bands. I have a rig very similar to the picture here and it works great. If the shield isn't cutting it alone, just put the furry on.

I purchased a stereo Rycote (AE) and stereo connbox when I first picked up my Schoeps MS pair years ago. It worked great and was the recommended size for these mics, but I was bothered by the fact that it is practically the size of a watermelon and there was a ton of empty space in there. I've since changed my rig to a smaller mono windshield. A bit of a compromise on wind protection, but it was worth it in portability.

If size is really an issue, I'd recommend looking at a Schoeps ccm MS pair. They can fit in a a mono ballgag no problem. Plus the ccm 41 is a great production dialog mic.

PS: Don't gaff the mics together. Use these back to back clips.

Before I answer, let me say that I have several single mic Rycote systems and 1 stereo system.

No, you're not really going to be able to fit two mics into a WS4/WS2/or whatever size you're buying. [Not in a Rycote anyways. Maybe in a Sennheiser kit, but that's about the same cost as Stereo Rycote with appropriate Connbox.] Unless they're completely imobilized, your going to have at least one of them bump into the windscreen anytime you move it...and if you immobilize it, you're effectively negating the shockmount. In all likelihood, even if you did just gaffe tape them together, the mic on top will probably just end up rubbing against the inside of the shell. Additionally, the Connbox you get with the standard kits are for one mic only, and you can't mount two Connboxes to a single rail.

There are stereo Conn Boxes available. Yes, they are a separate purchase from the stereo kit (the Connbox 3, and they're more than double the price of a Connbox 1).

I say shell out the cash for the stereo kit + connbox. It's expensive, but you get what you pay for. It's a great piece of gear. It's also the right tool for the application. The wrong one will just cause you aggravation.

You can use double clips to secure one of the microphones to the other. There are windshield kits that are big enough to allow such a set up, how big is the one you have?

For an example, see: http://frogrecordist.home.mindspring.com/docs/ms_setups.html

Thanks for the feedback, SSDers. I've kept the Rycote and managed to record crowd and ambiance from the Sacramento student Rally. Mind was not lost.

Let me also chime in as an owner of two stereo Rycote AEs. One for a MKH 30/40 pair and another for an Mk4/Mk8 setup. You can certainly get away with Schoeps in mono suspension but if you are doing heavy cueing (movement) you are likely to bottom them out in a mono suspension. If you are doing a lot of running and gunning I wouldn't recommend it.

I have done that very thing with a Rode Blimp. I used an Earthworks pencil cardioid and an AKG414 for my figure 8. Suspended the Earthworks in the blimp, and used rubber bands to suspend the 414 below it with some cut up foam windscreen material between the two to provide some mechanical isolation. Worked like a charm.

Edit: I wrapped the upper lyre bands over their screw posts twice, effectively shortening the length of the top bands. That gave me the height and the extra strength on the lyre that I needed to get it to support two mics.