If there's no reliable way to do it to get rid of the nag notification, the quickest alternate solution I could think of would to exclude 2560x1080 (for 29") and 3440x1440 (for 34") as options, since both will scale wrong and the 16:9 ratios rezzes put the side bars already. The 16:9 equivalents would be regular 1080 for 29" and 2560x1440 for 34". The nag notification's not as important as the scaling issue, as I'm sure the former can be shut off within the OS properties somewhere.