Sorry, I still haven't been able to settle down and do a detailed mod guide, but I think you already figured most of it out.
Probably the last step you'll want to take, I think, is to employ a piece of foam like so:
That's it. It'll allow bass to get that last percentile of tightness, IMO. And then it should sound like a more neutral headphone. But please be aware that this will also expose the sub bass deficiency of the original design. Engaging bass boost will now actually sound like it's giving you that extra sub bass, and the quality doesn't suffer. I think this is the best of both worlds, because otherwise, stock bass may be too much in some cases, while bass boost is simply ridiculous.
Edit: oh, and also nice side effect of better isolation since noise from bass port is mostly blocked out, but some air is still let in.