I’ve had full suss for the last 14 years as a main bike but remember the good ol days when I rattled around on a ’99 Zaskar LE. That was a hard and very direct ride.
Having bought a C456 frame and built it up with 140mm revs I would say it is nothing like as harsh as the older Zaskar and is a very nice to ride bike.
Before that I had the original Ragley Piglet frame and that was great downhill but rather dead feeling on anything other, and I also has one of the first Marley frames as a replacement from Hotlines when I sent the second Piglet frame back because of paint issues.
Never built the Marley up as I didn’t have the right kit at the time, but I’d say it looked very substantially built and a world away from the previous Piglet.
Am still tempted by a Soul or something similar to give steel another chance, but ultimately I’m very happy with the C456 as a hardcore (ish) HT at a good weight.
I’m 17 stone and rattle down things quite hard. It hasn’t complained once yet, so I don’t think the OP has much to worry about strength wise.