I've run straight perlite as a hydro medium before in my waterfarms and in netpots before
It works just fine, but as said it doesnt support the plants weight worth a shit compared to coco/pro-mix. Definitely need a main support stake or yo-yo's, a trellis, something, anything for support
Also you will have algae growth on the top of your perlite if you do not have adaquate shade cover from your plant. Turning your beautiful white perlite algae green, yay!
As a medium it works great, there is just better mediums out there for hydro IMO. If you cant lift all that hydroton though due to some medical reason you could make do with perlite. Janus, a member here, seems to do real well with JUST perlite as a medium
I'm currently back to hydroton, IMO hard to beat for these netpots
And btw you will be suprised how much water perlite will hold, l was. Take 2 - 5 gal buckets with holes, fill them with perlite, leave one bucket dry and light, wet the other down till water runs out the bottom, let it all drain out, now FEEL the weight difference, the perlite does hold quite a bit of water actually!