SWC's and mushroom compost

Has anyone tried using mushroom compost in self watering containers...specifically Earthtainers?

I grow cukes and tomatoes in SWCs/Earthtainers in a greenhouse setting using Ray Newstead's design (Much appreciated Ray!), going with his recommended 3-2-1 soil mix.

That is...3 parts potting mix (with some added composted manure to charge it up)...2 parts bark fines....1 part perlite. I've read a lot of material on the TV forum regarding water absorption and soil compaction in SWCs, and have been careful over the years to try and recharge my mix as described in Ray's Earthtainer document.

As we have access to SMC (spent mushroom compost), I was wondering if it had any applications in SWCs?

Has anybody tried it? Thoughts on issues?

Thanks
B