That's why I like internal bungees. The only lip required is the one for the gasket. It can be as narrow as a 1/2" making a more usable hatch opening.

While your system may work fine, the reduction in the opening size is a something people should consider.

Yes, I agree, if you must stuff large objects in your hatches, using magnets will require a smaller final opening. You could use more smaller diameter magnets and have a larger opening. I've never had a problem loading gear for a week plus trip.

I often use my hatches and fill the spaces totally with gear. I find smaller hatch openings easier to stuff gear in tight for long trips. And the magnets are strong enough to compress gear sticking up in the hatch opening and apply even continuous gasket sealing pressure around the whole hatch edge.

I feel the shock cord and internal fittings would get in my way to load gear and move it around in the hatches. I'd find loading up the compartment and holding onto the loose end of the shock cord inconvenient. Certainly if you rarely carry gear this isn't an issue.

As hatch openings get larger, they are more likely to leak and require a better hatch to deck fit to compress the gasket properly. I'm surprised to see you only have two center pull down points on your hatches, thanks for the photo.

I guess we all learn to love our own designs. I like the wider internal deck lip. It looks strong and adds great stiffness to the deck. And it's a design feature, hiding the deck lip magnets under a fancy veneer looks great.

I do agree with you about tethering hatch covers, I like narrow webbing with a fastex connector to fix, yet allow separation of the hatch cover if desired.

All the best,
Rob