Loft Boarding

Looking at boarding the loft for easier storage as when I moved in there was a stack of loft boards. I have added insulation last year but decided to partially borad it roughly just down the middle. I think this is between the struts. I'm not too worried about load just some clarification hopefully or start thinking again.

Planning on putting Kingspan between the joists around the hatch so it doesn't lift the floor height too much and its still easy to get into, this will have boards over and screwed down. Planning 100mm Kingspan, reading I may need to put 50mm on top as well. This will only be about 1m around the loft hatch. This is my worry as I don't know if I need an airgap or not?

The remainder will be 300mm loft legs to make sure I keep an airgap above the existing insulation.

Will be bonding some kingspan to the top of the loft hatch.

Lastly as this is what I think is referred to as a cold roof is there any benefit in fitting superfoil or similar to the underside of the roof.