Most of the openback banjo players in my classes don't use an armrest but I need one for comfort and arm control. The Deering Goodtime only has 16 brackets so it can't accept all armrests. I tried a Vega style rest on it for awhile. It was thin and high and very uncomfortable for me. I wish I'd known at the time that the Vega rests can also be mounted flush against the tension band as shown in thread cited above.
Since then I've tried a couple of different wood armrests with universal fit mounts on my Goodtime and here's how they compare;
I've been using a Nechville comfort beveled dark hardwood armrest for about 4 months and recently received a Slimline Tigerstripe curly maple armrest from littlemountainmusic.com. I was curious to compare the two styles of armrest for appearance, comfort and functionality. They are similar in cost.
Relative size and appearance: Both arm rests are about the same length, with the Slimline (¾ inch wide) about one half the width of the Nechville (1½ inch wide). The Nechville extends ¾ inch out from the rim and and is quite noticeable on a banjo without a resonator. The Slimline doesn't extend as far over the outside of the rim as the Nechville and is less noticeable.
The light colored and heavily patterned wood of the Slimline rest complements the light maple of the Goodtime. The Nechville rests are made from a dark hardwood which, depending on your personal taste in these things, either complements or clashes with the light maple of the Goodtime.
Attachment: The Nechville uses a very simple mounting method of two small Z shaped mounting brackets, each secured to the underside of the rest with a single screw. The open end of the brackets are slipped under the lip of the tension ring and tightened with a screw driver. The rest can be positioned anywhere along the head. It is simple and secure, the brackets are hidden out of view under the rest, and it takes about a minute to install.
The Slimline uses a couple of special mounting posts which slide over two of the banjo's mounting brackets. Flat ends on the top of the Slimline's mounting posts slide into a recessed groove which runs along the underside of the armrest. The rest can be adjusted about 1/3 inch up and down from the head and in or out from the rim, and is then secured in place with small locking knobs on the mounting brackets. It's a secure and adjustable mounting system which looks good. It takes a few minutes to put on the mounting brackets, retighten the head, and to adjust the position of the rest exactly the way you want it.
Comfort: The Slimline has a mild curvature across the top with slightly beveled edges. The Slimline provides a comfortable and supportive top surface, though at about 3/4 inch it's not quite as wide as some metal arm rests.
The Nechville rest slopes down at about a 25deg angle across most of its width leading into a more pronounced bevel along its outer edge. This provides a gently curved wide shelf of support for an arm which isn't held parallel to the head. The smooth curvature across the entire top of the rest allows the arm to slide very smoothly across the rest and doesn't cause high pressure points. This is a very comfortable arm rest.
Variations on a theme: Both armrests are well made with universal attachment systems that should work on any 11” banjos. I prefer the appearance of the Tigerstripe maple on a thin rest with the light maple of the open back Goodtime. The darker and wider Nechville armrest, by comparison, looks like it was made for the dark mahogany body of my Gold Tone GB250 and blends in with the dark resonator below it.
The comfort factor of the rest will depend on the combination of how hard the player presses their arm against the rest and on the angle of at which the arm contacts the outside of the rest. I normally press my arm quite firmly on a rest and against the narrow outer edge of the rest instead of laying my arm flat across the top of the rest. Due to their wide sloping beveled top the Nechville armrests are the only ones I've tried so far which are really comfortable for my own personal arm position and playing style.