Awhile back somebody had some photo of what you described, two carboys with hoses running to two 1-gallon jugs filled 3/4 full with water. (It was a beautiful photo.) So I think what you have will work.
Two things to note.
1.) Since its larger, much, much lager than 3/8 or 1/2 blow offs it will require considerably more built up pressure to blow the hose off. Which is very good. So its very unlikely to occurr.
2.) Since there is a lot more air in the hose and the fact that air is compressible you may have to wait longer to see if works or for that matter, leaks.
When you put it together I suppose it was wet? Let dry then see how easy it is to pull it out aftwards. The sanitizer might lube it up slightly.
If you are fermenting anything and you think its leaking you could put just a few drops of rinse-free sanitizer around the OD of the hose and watch for gas escaping by (shown with bubbles). This would NOT ruin the beer if it leaked back into the carboy if its rinse-free like One-Step and properly diluted Idophor.
Let's suppose it does leak. Get some Saran Wrap. Drop one small sheet over the top of the carboy (for protection). Then procede to wrap a couple layers around the hose, but not too many otherwise it would be too big. Remove the cover sheet and try to fit the hose into the neck. I think that would work.
I normally use a carboy cap, the one with two protrusions one for the airlock one for the blow off. Your method is a good alternative if you don't have a cap.