Couple of things:
First. Gorgeous uke. I've only seen a Poinsettia once and it was in a glass case but it was something. It had the pearloid fret board. I would definitely get the written documentation. Collectors value that sort of thing and it will help you get the best price for the instrument. Gruhn is a great resource. So is Matt Umanov in NYC.
Personally, I think the green bead flourish around the headstock might have some suspect. I have not seen this on any other photos of Poinsettias but it could be some sort or original addition.
Second: Am I correct in noting that you have now pulled the instrument twice from ebay? This will be a huge red flag for interested parties, I guarantee it. Even though you explained why in the second listing, ebayers are notoriously cautious and suspicious and when and if you re-list the instrument, I would suggest strongly that you clarify why the listing had this kind of activity. It will only help your case. Others want to chime in on this?
Third: This is a Gibson Poinsettia. Why not put that in the title of your listing? That would be a real magnet for collectors searching for interesting instruments.
I think that you are on the right track with this. Documentation stating that it is, in fact a Gibson Poinsettia will be a huge plus in the successful sale on this instrument. And, in my opinion, worth the cost of having it appraised by a reputable and known dealer in vintage instruments.
That example at Intermountain is really something. Beautiful. I troll their site regularly for cool stuff and have been for a very long time. That particular Gibson has been in their listed ukulele collection for quite some time, and at $7500, it doesn't surprise me. That is a lot to drop on an instrument.
Good luck with your sale. Someone lucky collector may very well wind up with a real jewel in their collection.
Mike