baskets are better than clay pots?

[Andrew]

For the size pot you're talking about, I'm not sure that the increased porosity of clay or net baskets would do a lot to prevent dead spots in the centre of the mix. You may want the 50cm diameter to give the roots more space to grow but do you need the 50cm depth? Have you considered a 50cm squat pot? Alternatively you could place an upturned 30cm pot in the centre of the 50cm standard pot to displace the stagnant mix at the centre of the pot - using an upturned net pot would allow for greater air exchange but unless you line the base of the pot with sphagnum or similar you'll find your peat : perlite falling through the netting.

Regarding your mix, personally I don't like using peat : perlite mixes for Neps. I have problems with peat mixes getting too heavy in medium and large sized pots. Nep growers in my area seem to favour sphagnum, usually mixed with coarse fillers like orchid bark to stop compaction as the mix ages. I've seen very healthy Neps in 30cm standard pots grown in this mix.