That will not be a problem. I use a cheap 25g tank / pump that sits in the loader bucket with a homemade 6' boom. For weed control, spraying is MUCH cheaper than any type of spreading / broadcasting product. Enjoy.
I would think you would be fine, I use a similar 25 gallon setup on my Bx25. Most of the time Im only making multiple 20 gallon batches and even 10 gallons, easier to calculate but have filled it to the top and have had no problems. Worst case scenerio is not to totally fill it.