Troublesome lens - any suggestions?

One of my larger adapted lenses a 150mm/1.2 for my 5x4 monorail doesn't have a shutter:
A challenging lens by Mike Kanssen, on Flickr

At about 5" across it's too big for any available shutters, and it's fast aperture makes exposures too short for the usual lens cap approach.
So far I have managed to get underexposed & overexposed shots (costs can rapidly add up shooting film uncontrollably!), using slow film & a reduced aperture.

I have some waterhouse stops made to give aperture control, but using an heavy lens like this I want to be able to try it wide open. :)

Any suggestions on approaches to proceed will be welcome!

DIY Guillotine shutter at the front? Slit variation included. Lartigue would approve!

That sounds like a workable option, not too complex...

Large Format site has some examples I think. Still have to think about the impact of releasing it at that position.. Counterbalance weight somewhere going the other way. Well I see that in practice the guillotine blade is kept in position by a finger under it and then released so its weight is free of the camera, floating in the air more or less, creating only an impact at the end of the fall.

You could use a LCLV (single-element Liquid Crystal Light Valve). It's basically an electronic global shutter going as fast as 1/1000s, but it isn't completely opaque when closed -- just about 9 stops darker. The Arduino library I created for it is:

github.com/aggregate/LCLV

There's also my paper "Programmable Liquid Crystal Apertures and Filters for Photographic Lenses" describing this at doi.org/10.2352/ISSN.2470-1173.2021.7.ISS-120.

A Guillotine shutter would be the easiest to make, but this is way more versatile. You'd still need a lenscap or other slow shutter mechanism to use with the LCLV because 9 stops drop in light level isn't really enough.

SK Grimes offers front mounted Packard Shutters for lenses like yours. They also machine nicely made custom waterhouse stops.

skgrimes.com/products/packard-shutter-mounting

skgrimes.com/products/waterhouse-stops

I'd looked at Thornton pickard shutters (which are similar to packard shutters but more available on this side of the pond) and never found one big enough.
I see packard shutters do indeed go big enough (I'd need 5" which is their largest regular size). The cost of these is rather excessive IMO, both the lens & the camera it's mounted on cost less than half the shutter. I suspect import duties & postage alone would be significantly more than the lens cost...
A top shutter speed of ~1/50s could also be rather restrictive.

My homemade waterhouse stops certainly won't be as smart or hard wearing as proper ones, but they are both cheap & functional.

Nice to see you made it safely over hear Hank!

That sounds cool, are LCLV systems available to 5" diameter at a (semi) affordable price? I've not seen any much above welding screen size (88x35mm viewable)
I suspect this would be beyond my technical abilities (my soldering sucks), but it certainly appeals :)

If I understand things right other non programmable timers could be used to activate the LCLV, a smaller version could still be a cool option for my smaller barrel lenses, where I might be able to get away with my current auxiliary shutters.
Mike