I understand your situation, Rich.
However, I can assure you that flatbed scanners focus very well on items on the platen, be it text on a document, or an unmounted negative/positive.
For 35mm stuff, my Konica-Minolta is far superior, for all sorts of reasons.
The V700 Photo is a very flexible bit of kit with its twin scanning options, lid and platen.
This is confusing. I agree that scanners focus on items that are layed on the bed, when you scan them with the regular scanning method - scanned from below as a positive. Of course, no one is saying you need to raise a piece of paper off the scan bed to scan it. So, sure, a negative could be scanned like that and it would work. I guess you could then reverse it in post-processing.
But, if you scan it using the slide/film scanning option, where the scan is done from above, the item has to be above the bed to achieve proper focus. It seems as though the entire operation is geared towards slide scanning, which are usually in the cardboard holders. So, a film negative has to be mounted in a holder simulating the regular slide cardboard to get the focus correct.
So, are you saying that you used normal, from-below scanning with your odd-sized negatives and then reversed them in post-process? I DO think that might work, focus-wise, and now am kind of wondering why I didn't just try that with a rgular ol' $159 scanner. In fact, I am now wondering why they bother with all those negative holders if you can just place the negative on the scan bed and use regular object scanning and then reverse the results. I think I figured that the exposure would be badly off, although you can adjust for that in the scanner. Total confusion...
Edit: OK, I have realized the problem here - it's a transparency vs a non-transparency. You need to use the above-the-bed scanner technique for transparencies like slides and negatives, whereas you use the regular below the bed scanner for pieces of paper, etc. So, you cannot scan a negative by just laying it on the bed and scanning it like a piece of paper and then reversing it in post. This is not to say that scanning a negative from above using the slide-scanner method will not work, but, as I've been saying, the scanner is expecting anything scanned with that method to be above the bed.