Originally Posted by Andy_Z

Yes, I think this the key question. Unloaded, I can usually crawl at about 3mph in my current lowest gear, which is 18 gear inches (3.21 mph = 18 gear inches * pi* 60 rpm *0.00095). If I recompute using my ideal cadence (90 rpm) at my minim speed without tipping over, I get 12 gear inches as a realistic lowest desirable gear. And interestingly enough, a 22 chainring 46t sprocket combo on my 26" wheels is almost exactly 12 gear inches. Seems like it is fated to be...

BTW, unlike paniers or bikepack backs, pulling a trailer doesn't increase the wobblyness-factor as far as I can tell, but contrary to other posts in thread, a normal bike trailer will NOT prevent you from tipping sideways. Good trailer mounts have three axes of rational freedom, but even ones with only two should be set up so that the bike is free to roll side to side. Otherwise you'd hardly be able to turn, it would be like riding a terrible trike