Speed Graf + Lens Board Question

Hello All- ive recently bought a good condition Speed Graphic and because of some awesome users on here, I now have a grafloc and a polaroid back. My stock body came with the Kodak 127 4.7 Exter.

Being that I mostly shoot 3/4 length portraits (with flash), I would like a lens in the 250 ish range but before I buy, I would love to get some advice on 3 questions:

1- What is the best lens I should look at for that length of portraits, with good shallow depth of field? Being that Im just learning LF, I dont want to drop a lot but at the same time I dont want a lens Ill hate (i only shoot portraits).
2- None of the lens Ive looked at come with lens boards. Will most lens fit the one i have standard? Im very confused about lens boards and the bore and all of that...
3- If Im shooting full lengths of people with my current 127 @ 4.7 will i have a relatively short DOF? I know this relative to a lot of factors, but Im not sure what 4.7 would be in 35mm (ive looked at it on DOF Charts, but i know that it the same DOF looks different on larger formats...

Anyways, thanks everyone for taking the time to read this post...Happy shooting!

Does your speed have metal or wood lens boards? If wood, don't worry too much. You can cut a board out of hobby plywood, cut a hole and paint it black.

Also, at 250mm, you will have shallow depth of field unless you use small apertures. 4.7 is relatively fast/shallow in this range.

When it comes to portraits, do you want a softer/older style? Do you want something sharp? There are a lot of choices out there.

If it's a speed with the graflok back (like you'd slip a polaroid holder into), you probably use the metal lensboards. Buy a metal speed/crown graphic board on ebay with the diameter hole you need, or buy a blank board or one with a smaller hole, and have someone make the hole bigger to fit the lens. Every shutter mechanism has a different size hole it seems.

Some sort of 210/4.5-5.6 lens would be good for 3/4 length portraits and be versatile for people pix. For flash, make sure the lens has a shutter with x-sync. If you divide every thing by 4 to get compare with 35mm, that'd be about like a < f1.2 lens. A tessar/optar/ektar (4 element) lens will be most versatile as they get super crisp when stopped down. The planar lenses (such as any 210 made in the last 30 years) are very good, and old lenses can go from soft to sharp with a twist of the aperture. And old non-shuttered lens won't work with x-sync, as you'd probably use the focal plane shutter of the camera, which doesn't x-sync.

Here's a 210 at f8-11ish, enough DOF for two people:
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And here at 5.6, notice the hair goes out of focus on the side
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