you can try reverse lunges off a box too. those feel way more natural to me. but split squats are great as well....really focus on driving off that front heel. you can also do bulgarian split squats....just a split squat with the back foot elevated....gives you more range of motion.
the static lunge is also a very good exercise.
it has shorter range of motion but is also less stressfull on the knees.
you can hold a barbell(EZbarbell works very well too) under/in between your legs also instead of on your shoulders.(safer when you cannot hold the weight anymore).
done this with 130 kilo.
I'm no Hulk but I do know this exercise a musclekiller.