None that I know of. I simply hold the gun, and use various blocks in my left hand to determine when the gun sits level. Once I trim the block to get level, I then cut or adjust the shaft on my palm rest to that length. Mine all have about 1"-1.5" of adjustment, so I need to get it close enough to use the final adjustment.

One other thing I forgot. My block usually has a V notch in the end so the forearm sits in it. It helps to have a 2nd person to put tape on either side of the block, once you've got length and position located. Then you can mount and cut the shaft to length.

There is a whole how-to book available on schuetzen shooting. It's available from the books page on this web site. To access it go to:
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The book is listed there, titled:
Loading and Shooting Traditional Schuetzen Rifles

Well today is the day for trimming and trial and error. 

Thanks so much for your help fellas.

Update:

Thanks a bunch guys for all the help. I trimmed the staff, and I feel it is still a bit long. But rather than continue to cut on it, I tried using the grub screw that governs the angle of the staff. I reckoned that if it had a more acute angle, it would effectively lower the rifle vis the left palm. I also tried raising and lowering the right elbow to lift or lower the back of the rifle to arrive at a consistent firing position. This technique is not all that effective I don't think. At least not enough to change the gross angle of things, maybe it would be helpful in fine tuning elevation once the base setting of the palm rest staff length were arrived at.

While changing the angle of the palm rest does lower it a bit vis the left palm, the rifle weighs a ton more with each angle increase. So I reckon I'm back to a more vertical staff angle, and cutting maybe 1/4 inch off and trying it again. As it is, the staff is bottomed out in the socket, which has tension screws one can tighten to sort of clamp onto the staff were one to find a happy place less than all the way into the socket.

I'm going very slowly here in effort to "measure twice and cut once" as Mr. Ross Perot used to say. 

Oh. Another question: I find that keeping my back straight is the most comfortable and steady position so far, rather than sort of scrunching into the rifle. However with an erect head position, I find that I cant the rifle a bit inboard. I had no issues doing this when I shot high power, as I could adjust the sights around the cant. The issue, of course, becomes one of assuring that the angle of cant remains consistent. I'm conjuring up a sort of bubble arrangement, rotated a bit around the axis of the barrel so that a quick glance would assure that the cant is consistent, shot-to-shot.

Suggestions or ideas?

As Boats mentioned, it's personal feel, and it's important to be as comfortable as possible once it's done! Keep playing with it until it feels right.
My guns with palm rests and Swiss buttplates all balance well when I'm holding them, and the buttplate is under my arm. I can open both hands and the gun wont fall or change position. So closing my hands doesn't require I grasp the gun tightly to hold it.

to get a little more elevation instead of adjusting your palm rest you can also open you stance a little more. Muzzle will go up.