Ive never done one but some mates do them so may give one a shout soon. Dont want to have to get another bike though.

I’d probably knock the Rev 150mm air fork down 10mm or maybe 20mm if i can so to make it a bit steeper and adjust tyres accordingly. I think its only about 24lbs in current 1×10 mode.

Is it too slack and or stiff for these 10hr + things?

You can ride what ever you want …..

I did laps of 10 under the ben last year on a fat bike ( long after we abandoned any idea of actually racing )

Did all my laps yesterday on a rigid singlespeed 29er

Ive done them in the past on a heckler and a 21lb xc race bike.

Run whatchabrung

Depends on your riding style, age, and what you’re used to etc. If you regularly do all day rides on it then yes I would think it would be fine.

One way to find out eh!?!

Is it too slack and or stiff for these 10hr + things?

Not at all, but you might want to reconsider the 1×10 unless you are fit.

You’ll definitely need a new bike.

Trail_rat +1

Well i could give it a go and find out as Paceman says.

Ive only just got it and just done 1 ride on the thing but it seems quite quick if not a little harsh compared to what im used to,

Pretty certain there were a few at yesterday’s.
To give you an idea, in my team, I was out on an Anthem, one team mate in a ti charge duster with every bit if carbon going and the other 2 were on 160mm bikes bought for alps riding. We all got on just fine.

I did the Dyfi Enduro on a steel 456 with 120mm forks.

You will smash your face off and die.