Not sure if you understood my comment but I do own an FX700b as well :). I just want to get a small extension cable that isn't to thick or thin and doesn't compromise the FX700s sound :P
I got some (don't expect Shure isolation though...) isolation with FX700 using Ts-500 Comply foams (Ts, not T).
Very comfy, and insertion is shallow enough so FX700s sound their best.
Sound wasn't modified when compared to provided large silicon tips.
Pros: cables are not detachable, but the strain reliefs are top notch (long and souple) so there shouldn't be any issue. And for the record, the cable is completely tangle-free and yet very souple but a bit short.
Cons: the connector is nothing special, and the provided extension cable is much lower quality than the IEM cable.