Contemplating putting 445mm rigid forks on a 29er (mainly cos I have some and do not have 29er specific forks. Bad idea?

Tried it with cross tyres on the wheels and seems to work well, sharp steering. Will it be any different with 29er tyres?

It should slow down the steering a touch, as the trail figure increases due to an increase in wheel radius. If it's monster-big tyres you might notice… (though it should still be quicker than stock).

Obviously your BB will raise up to closer to where it's intended to be, but will still remain lower than stock with a 465/470 fork, and tour angles will be almost a degree steeper than intended.

What bike is it?

On one inbred 29er. With the cross tyres steering felt no slower than my 26er. Cross tyres are way lighter than 29er tyres though, and the lower BB probably helped stability. Will put on Specialized Captain 2.0s.

Will the steeper angles make it a harsher ride?

Harsh in terms of comfort? No.
Harsh in terms of a lack of handling forgiveness? Maybe….
The 445 fork/CX tyre combo is the most harsh you could manage though – esp when combined with the lack of traction that CX tyres offer!

Glad you asked. I'm intending to do just that: putting 440mm Pace RC31s on a Kona Kula 2-9 until I can afford some travel. I've seen Mr Worland at WMB put them on a 650B before but hoped a 29er wouldn't be a step too far.
(Anyone got any 29er forks going?)

what are the forks you are contemplating using Picto?

I have 450mm Orange F8 steel forks on my inbred 29er. It handles fine, and has a nice low front end.

White brothers. They were nice and compliant on my 26er so hopefully they will be up to the job on the 29er.