The material Kelty used on the D4, Tioga, etc. is generically known as "pack cloth," and is about 7-8oz. per square yard, 400-450 denier, and PU coated. It wasn't a ripstop weave, and didn't need to be, since it's fairly heavy.
I'd suggest the V46 polyester thread, also from Seattle Fabrics. Most home sewing machines won't handle the V69 well with coated fabrics. "Regular" polyester thread will work, too, with maybe some extra stitching for reinforcement in places.
You could use lighter fabric, though, like the 210d Robic ripstop from Ripstop By The Roll.
I've made several internal-frame packs with 70d ripstop. It's not nearly as durable as the heavier fabric, but OK if you take care of it. On an external frame pack, I wonder if the 70d wouldn't wear quickly where the bag contacts the frame crosspieces.
On the Kelty D4 frame, the grommeted flaps that fasten to the frame would need to be reinforced, either with extra layers of fabric or maybe some thin webbing.
Regular grommets will work...I've made several packbags for external frames and had no problem (with heavier fabric.) Spur grommets were used on the Kelty, and are better, but the setting tool is expensive.
Always remember that you are absolutely unique, just like everybody else. -Margaret Mead
Our long-time Sponsor, BackcountryGear.com - The leading source for ultralite/lightweight outdoor gear:
Affiliate Disclaimer: This forum is an affiliate of BackcountryGear.com, Amazon.com, R.E.I. and others. The product links herein are linked to their sites. If you follow these links to make a purchase, we may get a small commission. This is our only source of support for these forums. Thanks.!