Joop, I've had a 29er Velocity P35 with 2.4 Ardent tubeless for a few months now and I'm really impresssed. I can ride this combo at 18-20psi and the cornering grip and comfort is great. It rolls in the rough easier too which is a benefit on a rigid bike. I don't notice the added rim weight.
So yes, 29er tyres do handle better with lower pressures supported by a wide rim. This was advise I got from a well-respected frame builder and he's 100% right.
Have a look at Flows / new Pacenti 28mm rims as a minimum, or as an ideal the P35, maybe a kris holm.