I use a Hawkeye with a 90 degree eyepiece fairly often. I would not be without the adapter. Once I figured out the best way to use the tool, it became quite simple and easy. For rifles that are not glued in, I lay the barreled action on a table so that it is parallel to the edge, and use magazines to elevate the action and muzzle so that the centerline of the barrel is the same distance from the table top as the radius of the adapter's snap on ring. I mount the light, and turn it on, remove the protective sleeve from the optical tube. and carefully insert it into the action, through the chamber, into the neck part of the chamber. I let the light lay on the table, and handle the scope with both hands on the eyepiece end, with one hand on the piece that rotates the mirror, and the other on the eyepiece. By having the barreled action, or barrel in line with the scope, and both supported from the same surface, the risk of damaging the scope is significantly reduced, and because I am in a comfortable position with good control of what I am seeing, I can take my time, and do a through job. If an action is glued in, I remove the barrel for scoping. The only other issue is the barrel rolling, and to prevent that, I slide on a low torque barrel vise near the muzzle, and set the nuts finger tight, and then do any leveling the same way as above.
