I forgot who suggested double foaming, though I finally decided to give it a shot on my Smabat ST10s Gold. It found that the increased seal really helps run these at lower gain, allowing for some more bass as well as more noticeable mids. I'm definitely happier with how sound as now I can get vocals at a loudness where I don't have to worry about the treble spike. The additional warmness is a little less then optimal, but at least it sounds less peaky now.
Also for anyone struggling with donuts, I found it helpful to pre-stretch then pull the entire thing over the bud. Then slowly pull it over the rim of the bud before using my nails to pull out the surrounding rim.
If you find 2 layers of full foams makes the sound too warm, you can try putting a donut foam or a silicone cover as the inner layer, while keeping a full foam as the outer layer.