I think the dimensions you listed will be fine. That works out to 13 cubic feet. My current cage is 11.5 cubic feet and seems big enough for my two boys. Hey have area's that they enjoy and gravitate to but can still jump around.
Also toys and pouches in the cage can create a lot of "artificial" space. Hope you don't mind if I recommend some cage dressings.
I got this kit from etzy www.etsy.com/listing/595008229/sugar-glider-cage-set-rat-cage-set-sk?ref=related-1
(well a different color, but I couldn't find it)
It's a great value and I would recommend it for new owners. The stuff is all well made, I've machine washed them a few times and they are all holding up great.
Also my boys really like this www.thepetglider.com/collections/fleece-toys/products/playcube-fabric
and have enjoyed this www.thepetglider.com/collections/toys/products/trampoline
I typically switch out what I have in their cage every few weeks (except the cube, that is always there because it is one of my boys' favorites) to help spruce it up. I think it makes for a good size and variety for gliders to be comfortable and happy. (I do have my eyes on a larger 20 cubic foot cage as an eventual upgrade, but I feel like my boys are happy enough with their current cage, so I'm not too worried about it.)