I have just finished building this old boat. Dating back to the 1980s, the molds are showing their age. Lots of flash-the railings are too thick for the scale-the deck does not lay down properly, the sail is very simplified and the armament is bordering on plastic blobs-the general shape is good, but lots of inaccuracies.
I would suggest contacting Nautilus Models (www.Nautilusmodels.com) and see if they have any of their resin and PE kits left specifically designed to fix this old kit up (TYPE VIIB U-Boat- 1940/Kit U-01)-This kit works wonders as you can chuck out all of the malformed plastic and replace it with resin and PE.
As I am not too great with PE, I used a combination of kit parts and the mod parts.
The kit railings are a tad difficult to remove from the sprues because of poor molding-try cutting them away with a small saw, then shaping with small sanding sticks and SHARP Xacto blades
I ran into the same problem with the main deck-in my case I carefully sanded away the deck section where it slides under the hull at the bow. Lots of test fitting/sanding and it finally lay down smoothly.
The old Revel Germany U-99 will give you a decent representation of a Type VII B, but if you want more than an advanced toy, it requires aftermarket parts and fiddly detail work.
Jeff J