Agreed. Still nowhere near the Kyosho big bores or even the Kyosho standard bore velvets. I don't think it's an issue with the springs, though big bore springs are pretty popular nowadays. Kyosho, Avid, Losi, but I haven't heard of X Springs. Will check them out. I'm looking forward to trying the Losi big bores on my XX-4.
As for the chassis, I've got the CF reinforced chassis with the battery slots on now. Can't wait to try the updated High Traction chassis that comes with the DB-01R. No battery slots, and they replaced the CF fill with fiberglass for more flex. I don't know of many that run carbon/graphite reinforced plastic chassis on anything other than turf. For dirt, everyone has replaced all the high-dollar, factory team option carbon/graphite plastic with the stock stuff. The new AE +8 chassis doesn't even come in carbon/graphite, and I think even the new WC kits from a variety of manufacturers sticks with the more flexible (some sometimes beefier) "stock" plastic.