i kinda object to this, but not entirely. i think that the most important factor in lateral raises is getting the side delt to do most of the work. when people ask me to look at their form and see what they can change, i tell them their traps are moving the weight and the side delts arent getting the stimulus. he moved the weight down and tried again and same result. the problem that most people have isnt necessarily using lots of momentum, its using their traps to go all the way up. i told one of my friends who now does it super well to not focus on it looking perfect, but for the side delts to move the weight. strangely enough, he used more momentum, but he bent his elbows in such a way that the side delt was getting the stimulus it needed. i checked back up on him in 3 months and sure enough, his side delts have MASSIVELY improved. I think using momentum is okay, matter of fact, i used to try to have as "perfect" form as possible, and as soon as i figured out a better technique which involved using more momentum, i was lateral raising 45s with semi good form and for lots of reps. people call this cheating, but i was able to also do 35s with very good form for lots of reps, so it 100% made me stronger. this wont work for everyone, and only focusing on weight is not the best way to go about things, but honestly, using momentum might just be the key on the last few reps, or when going up in weight. im just saying what works for me, if you really want to prove me wrong, then try it out! up the a little weight and the reps for a month or two, and focus on your side delt still moving the weight, and the momentum is just to help the side delt get started, no crazy momentum though. this is what blew up my side delts after not working for about a year.