We always try to install them in 4-post racks, but this week we had an install where the rear posts have been delayed.  The switches we installed have 2x 1100WAC power supplies each and stacking cables so are as heavy as they can be.  They actually sit better in the rack than the 3850s they replaced.  Therefore I'd say you can install them on front rails only, but if you can support the back I'd recommend it. ... View more