The lens hood has two threads.
One for fitting the hood onto the lens, that's 49mm and one at the opening of the lens hood that's 30,5mm
I hope that make things clear.

The DA40mm has a very strange hood.

This might explain things, the round thing in the right lower corner is the lenshood

I'm with Ken here with this matter.
You might get some shot because you've the range but you will also miss shots because the lens is slower.

I had the DA18-250 but sold it to get the DA*50-135. I was just getting crazy about the amount off range and I couldn't see the shots any more and the slowness of the lens wasn't helping

Terry how do you intend to turn the hood?
screwing it on and off?

Yes like the others say there is no way to turn the CPL when it's fitted inside the hood.
I use a 49mm one and screw on the hood on that and that works fine.

You only come to that conclusion if you see Filming DSLR as a replacement for a real camera but I don't think you must do that.
For real video nothing is better then a real camera but surely a filming DSLR has his place to capture video but you must take another approach I think, more like taking a moving photo.
I only have very little experience with the K-X but I think I've make some fun clips with it that way, at least they are different then your standard video.

They have versions on size as well, simply look up your screen size of the K-X and get the one closest to it.

By the looks of it the Ricoh XR Speedlite 300P has the same mount/contacts as Pentax.

I would just pop it on to see what it does, but that's me though and I'm known not to be too careful with my equipment.

You can brighten the screen, don't know if that will help

That doesn't really matter it's a product intended for the USA market so selling it here (EU) would make it a grey product and I don't know how Pentax deal with that. You better contact Pentax before buying.

Gwyn I didn't get you either at first but now I see, how it's explained differently maybe that helps.

car after 1 jan 2005
petrol and/or electric = 1x 4 years, 2x 2 years, every year
Diesel, LPG or different = 1x 3 year and then every year

car before 1 jan 2005
all cars = 1x 3 year and then every year

30 year old car = once every 2 years

before 1 jan 1960 = no MOT

The flash use the standard hotshoe so does Pentax for their flashguns.
The trigger voltage also seems low enough, Pentax once shimmered through it's confirm with the ISO standard and that's 24 volt link

You can't however not use any automatic modes on the camera with this flash.