Double shell jumps are bad ideas under any circumstances (I hate them personally and they hate me).
Well, looks like I'll be telling an amazingly old story about Kaizo again, starring: The Purpose
. (Oh no he isn't going to... yes he is)
The purpose of Kaizo is not to be hard, it is to have fun while exploring the very limits of Mario games in terms of playability. If people are interested in debating this with me do it via PM please
So what you should be asking yourself constantly while making a Kaizo hack is: "Is this fun or did I go insane?". A quick method of finding out is playtesting without any form of slowdown, since that is what players will be doing.
Unless ofcourse your entire hack (here; one level) is intended to be played with slowdown, such as Pit of Death. In that case you can test with slowdown.
: Can you perform double shell jumps without slowdown, and is it fun? Or are you submitting Pit of Death 2.0?
If you answered 'No' twice you made a mistake while creating your hack somewhere along the line.
WOW! I did't get ninja'd!
Of course you should fight fire with fire, you should fight everything with fire.
Oooh look at my userbar!
Sadistic Designer - testing Pit without tools.