trying all kind of tips and using the one that works best is what people should
always do. and not listen too much to what others say about it. for once I'm ok with the more than subjective opinions, because the shape of an ear can be quite a mess and need specific stuff.
also there is foam and foam, comply alone offers different kinds with slight differences in sound. the ones for sport fail at sealing(on purpose for the ear to "breath") so in a sense we could say it makes the sound brighter ^_^. and of course there is how people use them, because it's easy to have some foam to obstruct the output of the IEM and sound more muffled than it should.
in a side note, using something like the er4s(100ohm) is probably the best option given the pono's design, do you get obvious coloration or something sucky from low impedance multidrivers? the fidue a83 were getting the 10khz part a little annoying for me with my sony compared to using an amp (from rapidly trying them so I can't claim anything), is it the same here?
maybe it's so low in impedance that the pono starts to mess things up(negative feedback? no need!!!!!
who cares about having the right FR those days).
<= yes that's sarcasm.