Run a switched relay to the low beams. I've used hi/low in same bulb for many years with no problems. As far as legality, no different than driving lights. As long as you dim the high beams when you should, no one will ever know. Bulb life is not an issue, even when I was running H4s.

Curt B 89RS Calmini Header Delta Cam 33x10.5 BFG MTs & 90 Trooper 3.4 v6, SAS D44 ARB/Hobart 5.38s 35s my pictures