@Paul *********
There is no "black mark". I know people who do it a week late every time (because your next 90 day report is due from the date you apply and over the year you get a "free month" of time more OR at least that's their reasoning.
Immigrations doesn't care in the least if you get the 2000baht fine for failure to report, it's not a black mark, most people forget or miss the windown and get the fine once :P .
Some people don't even EVER file a 90 day report until they go for their new year extension :O , because the fine is just a straight 2000baht whether you're 8 days late or a year late, they just pay the fine, file one 90 day report, get their new extension and never go back to the immigration office for the rest of the year.
Each year they've been getting the failure to file stamps and paying 2000baht fine for many many years. It doesn't affect you at all. They believe paying the 2000baht fine is cheaper than going to the immigration office every 3 months :)