Spitpatch
I am not sure how it will fit on a Plainsman... but if you are considering a thang type peep site I would highly recommend the Lyman Peep. It is extremely versitile with the way it is set up. Push a button and you can raise and lower it to given ranges. It has a preset screw that you adjust for zero and from there the world is open to you. It functions 'somewhat' like the Quiqleys flip up tang sight - gosh i wish I could shoot like he did - I watch that move just to watch the shooting - I know it is not real but I THINK IT IS...
http://www.lymanproducts.com/lyman/s...ver-sights.php
http://www.lymanproducts.com/lyman/s...get-sights.php
This is one installed on my Renegade - you can see I did have to remove some wood from the stock...