I'm not height limited, but with this little 150w HPS I like to keep my plants as short as possible. Also, I've never been able to keep my oldest/lowest leaves happy with this little light, but it doesn't seem to matter. I've done a little thinning and she hasn't skipped a beat. It's a must with a 150w HPS otherwise I will only get decent flower growth on the top colas. I don't like to mention thinning because some get extremely sensitive about it.
Also your 5 week stretch was probably due to the fact that your AK47 is a sativa dominant hybrid? I'm growing a 100% Indica Afghan Kush.
I hear ya on the thinning, some folks are real sensitive about it, I took a flashlight and pointed up form bottom of canopy and if I saw 25% of light through that canopy it was alot so I had to do a surgical haircut. My plants responded nicely to it. Plus I looked up my other strain as well ( marmalate ) and both these strains do very well when pruned, my third strain does not do well in pruning so I left it alone (Polar Express) good thing she's a bit leggy so I just tied her down alot she comes in at 28" tall. For my next run I'm doing Kryptonite, my buddy just did that one, let me tell ya, that shit was slammin and I smoked plenty of good shit better than thai stick ( probably you too young to know what that is 70's ) I'm an old head.
I didn't want to leave you with the wrong impression. I had 3 weeks of stretching not 5, started right after showing sex week 2 weeks and ended at 5. But yes my AK is a hybrid, 70% Sativa/30% Indica, I chose this particular strain for its euphoric properties.
I use leafly.com to look up some strain properties, it seems strains from here you will find easy but you can give them shot, they're from Cali.
B4L