*Hanguard heat depends alot on the handguard design itself too.
Bonesteel and NEA/Troy both sit low over the piston and have no top ventilation -- narrow sides between upper and lower handguards and then substantial lower ventilation to allow air to circulate through the handguard.
The BC tactical
and Corwin/Zahal Czech Army approved handguards
both have substantial upper handguard ventilation.
The upper ventilation likely makes a big difference in handguard temp.
Whereas AKs' Pistons vent through the gas tube in front of the handguard, the VZ 58's piston vents beneath the handguard. The reason for aluminum is that it's light and softer than the receiver is less likely to scratch. Also, it doesn't melt (VZ 58s run hot b/c of piston setup regardless) and arguably provides a more stable platform for optics than does polymer.
A compromise either way.
However, add a Gas Pedal thumb rest and a Magpul AFG2, and your hand is pretty well isolated from the handguard itself -- or a vertical grip if you prefer and you're golden all around. Gloves are probably a good idea regardless, but considering that several of the above handguards are used on and with full auto VZ 58s, I think you'll be fine if you take precautions w/ your handguard setup.
Heck, even the top of the line 500 Euro, ~$600 US Antonin Zendl handguard is aluminum and has the least ventilation of any I've seen (some pics show top cover vent holes, most don't):
Your call on your rifle and roles you want it to fill, but for me, I prefer optimized mechanicals over keeping a handguard cool to touch.
I went with the troy/NEA because I like the low optic mount/ability to keep proper sight picture w/ factory stock (not having not upgrade that too) and that it keeps the lines of the factory furniture -- don't like the wider grip handguards and much more rails than I need w/ some of the other setups...
