Hi. The blown canopies are arranged by Airfix to provide builders with two options. There's one without a seam, that is the maximum size that can be moulded without a resulting seam and the other is the accurate one that goes beyond that point and so has a mild seam that you'll need to sand and polish out. I used this one on my test shot build in Airfix Model World. It's easy to remove but for folks who'd prefer not to tackle it Airfix have the 'no-seam' option. Looking forward to your build and others that'll start shortly on other You Tube channels. Wish you well with it!
I made the original Airfix 1/24 Spitty in (bloody hell...) 1970, or thereabouts, and the main issue was in the lack of dihedral in the wings, which completely ruined the appearance of the finished model. So I'm pleased to see a preformed main spar with correct dihedral, which will - hopefully - sort the problem!