How many SSC's per exercise progression?

I just recently started my third SSC on Advanced tuck lever and may max hold time went from about 15 to 50 secs. Is this a normal rate of progression? Granted I've bulked up lot since I started so that probably won't help, but I'm curious if most people take a few SCC's per progression?

It can happen! If your max time is 50 seconds of perfection, you should start extending your legs out a little on your work sets. That way you start working towards the straddle. This strategy worked well for me! I had my legs at 45 degree angles from my body both up and out, and after about a month and a half of that I was able to hold a good straddle for around 10 seconds.

Don't expect the same rate of progress, I was really really strong to begin with. Just keep going until you're able to hold that for work sets of 20 seconds, and then start straightening into the straddle inch by inch. You will get it! It can absolutely take several cycles to get past certain progressions. You have to remember that the stronger you get, the slower subsequent strength gains come. Be patient and keep working at it and you'll be there!