I think this is a bad idea. 7-8PM is the end of the day.
Sunday is usually a relatively slow news day. If the Nov11 contributions are huge in the early hours it could get coverage from news outlets tomorrow spurring even more donations. Lumping a whole bunch of donations in at the end of the day won't make any news broadcasts. You want to test the system or go for the most in an hour? Every donate at midnight.
Oh and this whole point is moot. There's only 2000 Nov11 subscribers. On Nov5 there were 40,000 donors in a 24 hour period. Over 1600 per hour. It's unlikely that Nov5 donors would break that rate even for a single hour - meaning the test won't occur and the 'most donors in an hour' record won't be set (not that anyone has ever tracked that number anyway).