Should it be minimal surface area on narrow rails or the wide contact aka the baking tray?

I've made a sledge from wood with narrow rails on aluminium strips but it doesn't go as well as I'd hoped. Will waxing the rails make much difference?
I'm contemplating adding a couple of runners up front to give it more girth at the front of the blades. Similar to the plastic blow moulded designs.

perhaps make it as wide as some skis.

Minimal width as it works by the pressure melting a thin layer of snow and the runner then glides on the water. Kids trying to use bodyboards were obviously unaware of this!

I made my runners from 1" x 1.5" wood (running on the 1" surface) and simply melted wax over them, warmed it with blow torch and skimmed with off cut of wood. Worked pretty well but after 2hrs use will require a little more wax 🙂

One downfall mine had was only 1.5" ground clerance, has been revised now but was ok on smooth slofes but not in powder!

Might see about some copper strip to glue on there 🙂

SSP

Narrow for decent runs. Wide for powder.

All depends on the snow you are on.

Compare skis designed purely for piste skiing to off-piste.

Soft snow – more footprint required. Blue ice – skates will work (as you describe above, melting the contact layer).

You can't skate down a snowy hill.

Try lining the faces of your wooden runners with formica. I did that once – my mate broke 3 ribs and got concussion.