I'm just in communication with a prospective buyer for my DL1608, he has an old iPad 1 so I asked him to try to load MF. The result is that iTunes says no, needs iOS7, the iPad 1 is no longer supported etc. So that appears to be that.
The next step has to be jailbreaking the iPad and seeing if somebody can break the DRM on MF2.1.1 (again, I will post a link to my copy if necessary). If anybody has a jailbroken iPad (of any flavour) perhaps they can see if it's possible to load a copy of MF2 not DRMed to their iTunes account (I may even try myself if I can make the time). As it is I've probably lost the potential sale but if there's a way to get these old but serviceable iPads working that can only be a good thing.