Sturdiness, grace, & utility of peep sights?

If you have first-hand experience with New England Custom Gun Service's peep sights that mount on telescopic sight bases, or XS Systems' Ghostring aperture sights, please describe the experience. More helpful for me is to include some way for me to contact you to better pick your brain.

The specific sights I am interested in are: EAW-Peep; Weaver-Peep. Here is a link to NECG's peep sight page. http://www.newenglandcustomgun.com/index.html?Peep%20sight.htm~maindeal

My alternative to the attractive Weaver-base aperture (with tiny mount screw, not behemoth shown) is XS Systems' (aka Ashley) ghostring sights. I particularly appreciate those, such as one for M94 Winchester Angle Eject that mounts perpendicular to bore. Here is a link to it. http://www.xssights.com/photos/205.jpg

My intention is to use [one of these] aperture sight assemblies as primary sight for three built-to-order muzzleloading rifles. XS Systems offers a particularly unattractive ML sight that is designed to fit on octagonal barrels. This sight will not fit my rifles -- thank goodness -- so I am not forced to choose it.

Since the area of the rifles' breeches where an aperture sight would be mounted can be profiled however I request, a sturdy, graceful, adjustable aperture sight is what I want. But I have no experience with any of the three sights I mention.