Going to do a small 1 gallon batch of cream ale for my wife, and wondered if there would be any REAL issue of fermenting it in one of my 5 gallon glass carboys? Issues/concerns?
no problem with doing that. It's not ideal with that much headspace, but keep in mind that world class beers have been made for centuries using open fermentation. I've made small quantities beers in vessels that were "too big" and never had any issues.
The only issue I can see is that it will be a little tricky to rack into your bottling bucket, as the 1 gallon of liquid will be spread out over a wider area, so you'll probably suck up a bit of trub, but that's not a big deal.