What I also wonder about at times is how deep Dunu intended the luna to be inserted?I preferred the Sedna Light Shorts over the spinfits. I actually liked them the best. I use size ML on the light shorts. We are all different especially with ear tips. You might want to try the Sedna Xelastec as that will give you a great seal. Most folks using them have needed one size smaller than usual. Amazon does carry them. Good luck
In my ears it often feels like the shallower the insertion the more comfortable it is (which is the case for most IEM's I guess) but as opposed to other IEM's, I don't always feel like deeper sounds better.