George you are correct, I am glad you questioned this.... I guess I should have gone to the source and asked Chris.
Now the question I will have to get answered, is will they do this kind of upgrade. I will get that answered for you on Monday.
This is the responce I got back from Chris Anthony.
The simple answer is "yes, they can be used together". George Kaye is correct in saying that you can install both if you add some additional sample RAM. Of course this would mean that you would need to load one of them (either IOP of Oriental), every time you power up the keyboard.
It's not difficult however to run both kits simultaneously in the same 8Mbyte DRAM, it's just a matter of deleting one or two voices that you won't miss and then they'll both fit. For example, the Arabic Kit contains 2010Kbytes of sampled sounds but only 321Kbytes of these are actually necessary for operation of all 16 styles. The remaining 1689K breaks down thus:
Aoud 1 524K
Aoud 3 314K
Aoud Tr 210K
The IOP only loads up 7907Kbytes of the available 8M DRAM (leaving 285k free). The IOP contains only one sound which is not used by any of the styles (Cool Alto) but deleting this would yield a further 440k of space. So now you have the IOP loaded, the Cool Sax deleted and 725K of empty space. That's enough to get the necessary sounds for all 16 oriental styles and at least one of the above voices loaded without needing additional RAM. If you wanted to get the whole Arabic Kit in, including all the sounds, you could remove one or two of the larger IOP sounds - substituting them with regular WK/SK sounds in the styles where they are required. For example, the IOP's "Rich Strings" is 1091K and "El Bass SK" is 625K. Just deleting and substituting these two sounds would give you space for the entire Oriental kit in one 8Mbyte DRAM along with the IOP.