I'd agree with the other suggestions Mark, it's not actually a great idea to be trying to get a perfect seal with these. I used Sony hybrids with them for a while, since they were most comfortable, but combined with their relatively small aperture and softness it did lead to a bit of bass bloat. The most recommended tips for these tend to be tips with apertures that are no smaller than the actual nozzle themselves - for instance, UE single flanges. I'm using some tip from god knows what, its either a Audio Technica tip or one of the original tips, I don't get a vacuum seal feeling like I do with the hybrids, and to me the bass isn't oppressive. Sure, they are always going to have to have more bass than treble, but I guess we're all hoping that you can appreciate what they offer especially on certain tracks. If not though, to each their own :) I have a friend who finds my DDMs too warm for his taste for example, and much prefers my RE0's. His favourite genre of music is metal, which is probably too fast even for the DDMs.
On a related note, looking at the Radius, the Monster Turbines and now the new insanely priced Sony EX1000's (really insanely mind you... at that price why not a custom?) it seems like dynamics are entering their golden age. I'd hate to see BA's disappear though - I hate seeing 'old but good' technologies get pushed aside, like plasma TV's for instance.
my own thoughts on the surge of dynamics is that ts a combo of them getting good enought as some are fantastic but thats its largely driven by a desire to move as much air as possible to satisfy the mass market element. those people who simply equate more bass with being the samo thing as better, bose, skullcandy, etc buyers. for my ears moving too much air just gets uncomfortable and ultimately painfull. its why i largely stopped going to pubs and clubs because i couldnt take the shitty quality stupidly loud music and levels of bass that actually made me feel ill.
whilre i can see the DDM as an interesting idea upon hearing it i just think its marketing gone crazy as the way its tuned there is clearly no need for that second driver. its subscribing to the more = better philosophy and this implementation simply is not. there is also just no need to have such a massive driver so close to your ear anyway to produce low notes. again i feels its marketing and "ooh sony did it" thats the ovor riding influence. im sure in time multi driver dynamics may take off but it needs to happens for acoustic reasons rather than bigger number = better mentality , be it driver size or the number of them.
i really dont see BA going away in the higher end however they will stay out of the mass market arena just as they pretty much always have