I Used To Use Halflytely Bowl Prep For Colonoscopy And

I used to use Halflytely bowl prep for colonoscopy and all was just fine. I just cannot drink a whole gallon of Nulytely that I have, so can I drink a 1/2 gallon if liquids run pretty clear? Because I don't want to put my credit card on an unknown site, I think I will just stick to clear liquids, no fiber, etc. 3 days before the test. And, if liquids run clear after 1/2 gallon, that should be fine. I have done this test 7 times because I had to start in my 40's because my mother had colon cancer (she would never take this test). I just cannot get thru that gallon anymore and I will not do a split dose - ie. SuPrep since my appointment is at 7:00 AM, and doctor wants me to take the second dose at 3:00 AM! Not me! No way.