MrP,
Excellent call on the silicone. I have a myriad of adhesives in the shop, one of which being a very good sealant that would also provide a smooth finish, but in this case silicone is probably the best option. Once it's in there, you never need to worry about it coming out. That's for sure.
As for the fit of the keel fin, not sure if this is a characteristic only of the new 900, but the fin has a distinct airfoil cross section which indicates the optimal (read: "correct") placement on the hull. The keel bulb also has a discernible airfoil shape at the fin insert which matches the direction of the fin as well. Fortunately, that arrangement matches the correct placement in your pictures, so looks like we're good to go there.
Lol, However, I didn't even think to look at how the decal placement matched the picture in the instructions. (It's the simple things...) Thanks for providing the pic as a confirmation! Actually, at second glance the instructions are very vague about that altogether. There are no illustrations at all that indicate any aspect of proper keel installation. There is also no direction in the text that points this out, and the pic on the front is barely adequate to use as a guide. This really leaves a lot to be desired for the beginner who might not have any background in that area; aerodynamic, keel fin design, or otherwise. To top it off, there are also no directions whatsoever telling you to fill the keel bulb in the first place, much less instructions on sealing, etc. I suppose that's why the fine folks at Hobbyking took it upon themselves to point out in the website product listing for the proud new owner to
"Please ensure you fill the keel ballast to 1.2kg or heavier. Lead shot, bearings or bolts/nuts will be sufficient..." Suppose you can't say they didn't warn you Tigertiger, I think you're right. It may be time for a review on this one, if for no other reason to quantify and help explain the shortcomings of the new manual.
If you gents can bear with me, I'd love to give it a go.