Hi there.
Geordie Geoff here (AKA Open-Cases), I have my vine (Black Hamburg) growing in my 19ft x 6ft greenhouse, what I would suggest (whether right or wrong) is to forego any fruit this year, for the sake of getting the vine trained to a shape in keeping with the greenhouse, I trained mine along the apex of the house, then trained spurs down the roof glazing bars alternatively, allow only five leaves on these for next seasons fruit, and keep them to this format, works well for me, and have been doing it this way for the last seven years, the grapes are 100% better than commercially grow, and you don't want to use chemicals if at all possible. Hope this is of use to you, even though it will be a little late for this year. Good luck
Geordie Geoff

P.S. the vine is 28 years old now