Fitting new MPK rooflight......sealant.

I've just ordered a new MPK rooflight after finding a chunk of my original has a sizeable piece missing. Fortunately it's the 280 x 280 one in the shower area so any rain coming through simply drains off into the grey waste tank. I can see replacement procedure looks relatively simple but wondered if anyone else has replaced theirs and if so, what sealant did you use? What's the best type/brand?

Sikaflex 512 is what I used on a bigger rooflight in 2016 and it’s still good

This might be useful:

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Thanks for the tips folks. I may yet decide to have it fitted as i'm hesitant about clambering up ladders in this weather to fiddle around on the roof....especially after busting a leg last year. I can't afford to risk breaking another bone now!