This may be too late to help DragonFly but perhaps it will help others.
The cleanest colons are those that had the last cleansing w/in 6 hours of the scope being performed. More than 6 hours and the gut is producing matter and chyme and passing it into the colon.
I have a TERRIBLE time w/these d*mn PEG solutions - nausea, vomiting, bloating; just too much volume of liquid in too short a time contributes greatly to my problem w/them. I so much preferred PhosPho Soda or Magnesium Citrate! *sigh*
However, my last scope my gastro convinced me to try Half-Lytely. AND she suggested I take longer getting it down. It worked!!! In fact, the first dosing had me running clear and if I would have had a morning rather than an afternoon scope I wouldn't have needed to "do" the second dosing.
Half-Lytely doesn't taste quite so bad. And I do NOT chill it as I've found the chilled just makes the nausea worse and chills me to the bone.