Can't say I'm enamoured of the angle measurement facility built into some of the more pretentious mic bars. The angle markings are etched onto such tiny, fiddly circular dials that - unless they have machined, detente click settings - a slight setting error is easily made and can pass unnoticed until the distances are extrapolated. (A weak analogy: no builder would use a 2" long spirit level.).
For most purposes, my go-to is just a clear-plastic, obtuse-angled triangular plate. By marking cm. or inch values along the long edge, plus a few key angle lines - 90°, 110° etc., it's easy to align the mic bodies properly by looking through the plate. And it's also handy for estimating orchestra angles etc.
Ach, but there again, nobody died from listening to a 113° ORTF recording recording. :-)