Attaining correct line will speed up your progress immensely in handstand and transfer to other skills. Initially when training with me some people will be devoting 80% of their training time in handstands to corrective exercises and only 20% to Handstand specific. I generally expect to have this issue fixed in 3 months with most people and then after that handstand progress is very rapid.
The following collection of exercises is what I’d use as a standard approach to correcting this issue its not a be all and end all but will aid most in correcting this issue.
One of the most common problems in Handstand training is trainees having an arched back and their ribs flaring. Inexperienced Coaches will automatically use the “ribs down” cue to try fix this, in my experience this is one of the worst cues for the situation as most beginner trainees in the handstand world actually do not have required scapular mobility to achieve the needed degree of shoulder flexion for a Handstand so rely on either arching the lower back or flaring the ribs to achieve it.
To know if this approach is for you I’ve come up with this easy to apply self test if you fail the test then this approach will more than likely help.