Stainless would be stronger than brass but its no gaurantee it won't crack. You really need to figure out why your freezing up, even up in the trough? Do you have heat in your trough? If not, you coiuld run a loop from your floor heat boiler or install heat tape in the trough. I have both....Aside from my truck bay freezing, which I believe was froze before the weep kicked on because of such a swift temperature drop, I had three other bays weeping cold water that survived -12° temps at night and -2° daytime temps for more than 2 days....(My weep sensor is currently inside a bay....it is getting corrected)... The 75' of Raychem Winter Gaurd Heat tape I have only uses 450w of electric. Thats not much for piece of mind....It gets to 120° and is self regulated. It never gets above 120°.
Even when my truck bay froze this time and it was a hard freeze, none of the brass fittings cracked in the trough. I have heat tape that goes all the way out to the truck bay, out the trough, and follows the HP hose down to the top side of the rotary union. Its all wrapped with foam insulation...The boom and union all thawed out on its own Wednesday even with temps not hitting 30°. If I didn't have the heat tape or loop from the floor heat out to the truck bay, the freeze-up would have been much much worse.