[Varyon]

Spider silk produced by magically engineered and controlled spiders is going to be at least as good as TL 9's arachnoweave (from Cutting Edge Armor Design, Pyramid #3/85), where the genetic engineering bit is only so that usable quantities of the stuff are produced (probably as extra proteins in goat milk, then spun by spinneret machines).

You may want to avoid going to that extent, however, as it will mean your "I only wear cloth armor" guy can be better armored than your typical knight. For my fantasy campaign, I intend to do things a bit differently, with typical giant spider silk being much worse than real spider silk, and only the most dangerous (and impossible to cultivate, as they are sapient and evil) giant spiders, the iktomi, produce the good stuff.

For that, raw silk actually has the same base protection as cloth armor, but is much more effective against cut, pi, and imp. Against cut, it functionally has half again the edge protection - DR 2 silk armor changes cut to cr out to 5 damage, rather than only out to 4. Against impaling, it gives the same edge protection as most armor enjoys against cutting (so out to 4 damage, converts to cr; note it still suffers the -2 to imp if it isn't layered, so the above assumes layered silk). Piercing is similar, but with the caveat that in my houserules, if piercing gets converted to crushing, it does far less damage - 1/4 for pi-, 1/3 for pi, 1/2.5 for pi+, and 1/2 for pi++. It also negates barbed, poisons, etc as described in Low Tech. Simply giving it the blanket +1 DR suggested in Low Tech is, of course, much easier.

"Normal" spider silk has WM 0.6, DR/in 12, and MaxDR 6. It has the same special qualities as silk, above, and also needn't be layered to negate textile's default -2 DR against imp. Note this means it gives comparable protection as iron against most threats (and actually better than iron against cut, pi, and imp) by weight, although it has much lower MaxDR.

Iktomi spider silk is arachnoweave, which I'm not comfortable reproducing the stats of here (see the relevant Pyramid article). It also has the same benefit against imp as silk, above (the fact it gets x4 DR against cut/pi overrides the complicated bits from above). Note that even against crushing this makes it better than orichalcum, although again it can't be made as thick (although maximum thickness iktomi silk is actually better than maximum thickness orichalcum against cut/pi).