Charlie,

Yes, I put one on my U-47 after I had built it. Takes a bit of engineering but not too difficult. I did not buy mine from Engel but rather a German company. (most likely the same supplier that sells them to Engel) Works like a charm, too. Just make sure you use the included silicone lube. Also, I leave my sub halves disconnected when it is on the shelf. That way, the inside gets air and the seal won't stick. It does have a tendancy to stick if it has been sitting together for a length of time. ( I know, trust me)

You can find a couple of pictures in my gallery if you want to see what it looks like. Just look for the U-98 Type VII.

Pete