I know it's a little late for some of you, but it looks like they are listening to your input:
http://nhraracer.com/apcm/APCMviewer.asp?a=49632&z=175
3. If a Sportsman category reaches quota and spots become available prior to the deadline of 1 pm PST Monday the week of the event, entries will be accepted if the competitor has sufficient grade points at the time of entry.
a. Example – SS for a National Event reaches quota at Grade 4, when the event opens for a grade 3 and spots become available in SS, competitors with a grade 3 will be eligible for entry.
b. Example – SG for a National Event reaches quota at Grade 3, when the event opens for a grade 1 and spots are available in SG, all competitors with a grade point will be eligible for entry.