This is where the top end hybrids of the early to late 00s come into their own, the specialized Sirrus carbon you can fit 40mm tyres with room to spare, it has FACT 9M carbon (same as the stumpjumper FSR from a few years back). This is the best 'gravel' road bike I could have hoped for, mudguard/rack eyelets too! I run it with 40mm corretec slicks that are around 370g
Additionally, the Globe Pro/Expert from 2007/8, you can fit 50mm wide tyres on them, I run two, one with drops/road transmission and one with flat bar and MTB based
I got onto hybrids with my 2001 Ridgeback Genesis Day 02, bought in 2002 and I've been using a flat bar for the majorityof my miles since. Now have 3 specialized globe bikes, one 50 mile old 'pro' in storage for down the road.
The original Globe pro I bought in 2009, used for everything including going up some of the lower slopes of the Alps, audax, offroad, commuting, utility and the last one is an 'Elite' (also wth cf seat stays/forks) that I fitted drops and mini Vs + road triple c/set and is touring focused but again has been used for everything. The above sirrus carbon I mention is a very special bike, silly light for it type, sub 8kg inl pedals and a Apex double, shimanon Ultegra 11 speed flat shifters ad some Shimano Pro carbon goodies. It's robust and has much of the qualities of the Globe but more road focused yet is fantastic for off/on road aside from the deepest of muddy sections.
There were a few high end hybrids, a Marin ALP, Trek 7.7FX and some others
I use 32/28mm tyres for the most part on the Globe and have gone down some horribly rutted routes even when the tyres were pumped up mainly for road use, the carbon forks/stays plus 27.2mm USE Alien carbon post help, the CF bars on the Sirrus and the Globe Pro add even more comfort over an ally bar.
The OP is fine with the carbon road bike, personally I'd try to get lighter not more robust tyres, I bagged some Giant PSL2s years back and are miles better than conti4 seasons, come in at 270-280g for a 28mm (comes up nearly 30mm on a 17c rim, more meat in the centre of the tyre, off centre join (not dead centre like most makers), sidewalls are more flexible and they roll significantly better than the 4S. I was so impressed I bought as many as I could find, Rutland had been selling them heavily discounted for £8 IIRC, I'd bought two as a punt then so impressed I went hunting for more. With latesx tubes, that would make his CB pretty much bang on for a bit of off roading without sacrificing too much on rougher terrain.
