"Weight classes are as follows: Lightweights 175, 200, 231, Heavyweights, 265,300 and SHW" from nastrongman.com
The two meets I've entered this year (one done and one coming up) follow this format. theyre both platinum, perhaps if you re only in gold meets, that makes a difference.
As for waiting to get heavier, i can understand that, and its your decision, but two things
1) doing my first strongman meet was hands down the best thing that happened in my lifting life this year. I met vinny dizenzo (800lb bencher) who was doing a seminar at the meet, he invited me to train with his crew and i havent looked back. I've put 20lbns on my bench in two months (i had put 20 on in the last two years.) I had a real fun time doing the meet. training for it was, ehh, i like the gyms liftes better than training implements, but the meet was fun. I was worried i would get crushed and shouldn't have been, because i was so focused on what I had to do for each event that I wasnt even aware of whether the other competitors were doing better than me or not. By the time i thought to check the standings right before the last event i was solidly in 3rd place, (out of 10) which I was happy with