It is BEST to start out with the crown set a little lower than where you want it to eventually settle.
This is because natural hide heads stretch over time and in response to changing conditions (humidity). The amount of stretching varies depending on the properties of the individual hide, how tightly it was mounted when wet, and the conditions in which it is used.
My heads are stretched twice in the mounting and curing process. That is how I set the desired initial height. This process helps reduce (but does not eliminate) normal changes that occur in varying humidity. Most will continue to stretch before settling to a reasonably stable position. So I think it is best to anticipate some stretching to avoid a situation where the tension hoop might eventually pull too low and bottom-out.
I apply Renaissance wax to the top of all heads as a protectant. This may have some effect on stability. Stained heads receive a coating of oil-based wood finish (in addition to wax). This probably has a greater impact on weather resistance than other treatments I've tried. Leather waterproofer sprays do not seem to have a lasting benefit (so I don't use them).
Lots of factors affect the "ideal" crown height:
True rim diameter. I find that rim sizes vary as much as 1/8" from one maker to the next. In other words so-called 11" banjos actually range from 10 7/8" to 11" in size. Smaller rims may need lower crown height.
Tone ring type and shape. The radius of the bearing edge of the tone ring (or the wood rim) - affects the crown height. For example: a "Dobson-style" ring with a large-diameter surface radius may use a lower crown than a 1/4" round brass wire hoop.
Tension hoop type. The cut-out for string clearance at the neck can determine how high the tension hoop can or should rise above the top of the head..
Other hardware. For example - some tailpieces - particularly those that rest directly on the tension hoop - may work best if the hoop rises above the top of the head.
Player preference. If you have specific requirements or preferences as to how high the tension hoop should rise above the head, please discuss them with me. NOTE: If the initial crown height of your new head is too low (ie: the tension hoop rides too high), it is possible to accelerate the stretching and lower the hoop. If you need to accomplish this, please contact me for more information.
Below is information on how I set standard "initial"crown height.
The rims I use are from Bart Reiter and Stew-Mac. The tension hoops are 9/16" overall height - with a string cut-out at the neck that is 5/32" deep. I mount them so that the top of the head is even or slightly below the cutout at the neck notch. That implies an initial crown height of approx. 3/8" - 7/16" (REMO defines that as low - medium) .
However, due to the nature of the process, there will be some unavoidable variance in crown height. And - due to differences in hardware and construction - these heads may fit your specific banjo a little differently than the rims I use to make pre-mounts.
FEEL FREE to discuss your requirements, questions, and concerns during the ordering process. Just send a message through this website or by email. My aim is to provide a head that fits properly and serves you well for many years!
The photo (below) shows how I set the initial / standard crown in my shop.