Yes, Double MS is probably the simplest way to get 5 channels. All you need is three mics (two cards and a figure eight) and three channels. The mics don't have to be Schoeps, nor do you have to use the Schoeps plug-in. The cool thing about DMS is you can record only three channels and derive the 5 channels in post; no need to mix the 5 channels live. DMS also uses only one mic stand, so it's as low profile as a stereo rig.
You can do DMS with four cards set 90 degrees apart, but then you'll have to record 4 channels or mix the L & R mics before recording to three channels. I use a couple of Sennheiser MKH800 Twins set 90 degrees apart to do DMS, which is in effect four cards at 90 degrees, and I just record all four channels. The Sennheisers work well in this situation, but they are not the low-cost solution. What you have with the four cards at 90 degrees is Ambisonics without the Z (height) component.
I've recorded DMS not to derive 5 channels, but to be able to select any M mic pattern in post by combining the F and B mics. Of course I could get a 5 channel mix from my DMS recordings at any time if I wanted to, and that's kinda cool.