Michal,
you're right to be proud of your work, it's absolutely good. I can't believe it's your first model; if so, you surely have a previous experience as modeller or you have a job in which precision is important. I think, a well-known little mistake in our models is the better help for the next one making.
I don't know Mantua's manuals, I've never bought this brand's products, but I've already heard bad reports about some kits of its.
Cheers
Trink