One day I may be able to swim a 200m or even a 400m IM but for the present all I can manage is a 100m IM, in which it is not uncommon to be disqualified in the fly leg for failure to recover the arms properly (my left arm drags in the water). Sometimes, probably when the stroke judge is lenient or of a kind-hearted disposition, I manage to record a time and my times have improved over the last few years from over three minutes to about two minutes and a half.
I had an interesting conversation about fly at my most recent meet with a young lady who is a good butterflier, and her view was that the failure to get the arms out of the water properly was not connected with arm strength or flexibility but with core strength and timing of the undulation. I thought her diagnosis made sense, so I have been trying to improve my undulation and doing lots of breaststroke arms with fly legs, one-arm fly and upside down dolphin kicking for backstroke, and even some front crawl with dolphin kick. It is too early to tell if this is having any effect on my butterfly but I figure that it can't do any harm and is enjoyable. Oddly, although it is my left arm that drags when I swim full-stroke fly, I am faster and swim with more ease when I swim one-arm fly with the left arm. I am right-handed but breathe to the left in freestyle (still working on the right side breathing and making some progress with the drill of superman glide transitioning to skate on left side). My right shoulder has slight stiffness, probably as a result of an old Judo injury, so perhaps strengthening the right arm and increasing its flexibility will help to solve the problem.
It would be really wonderful to swim a 400m IM long course, but of course that must wait for progress in the butterfly.