Sprite of playable character - sheet 1000x1000 pixels divided into 10x10 frames.
To correctly fit into original SMBX's hitboxes, I recommend use the Playable Character Calibrator (use button "Image Calibration" where you can move frames on sprite to take fit it into SMBX's hitbox):
http://www.smbxgame.com/forums/v ... =69&t=6180
Note: you can use "Animator" to preview your sprite in action before test them in game
P.S. how sayd Chad, don't edit hitbox properties because SMBX have statically defined hitboxes which we can't change (just to make player more fat or more higher, or change GFX-Offset). But, now able with LunaDLL change width and height of player, but GFX Offsets now impossible to change (is not researched yet)