FWIW, I tried the Vltor A5 set up for a while, but could not discern any difference in recoil, function, etc. from a standard carbine buffer, tube and spring. All I got was a higher cost and some difficulty in procuring the right buffer. I ended up buying the latter from an outfit called heavybuffers dot com.
Later, I switched to a standard size Vltor receiver extension known as the "5-position" model, paired with a one-ounce buffer and reduced power carbine spring from Taccom to go with my low mass carrier and adjustable gas key from Rubber City. Excellent workmanship on the buffer tube, Vltor makes good stuff. - CW