About:

Mario & Luigi - Partners in Time Hard Mode 1.0 is a proof of concept hack that doubles enemy stats to create a more difficult game.
At this time, enemy items and character stats/level up bonuses have not been changed.
Story and maps remain the same, as do events.

Ways to play:
Tested so far on DeSmuME, but this should work on flashcarts and on Twilight menu.

How to patch:
Apply this patch to Mario & Luigi - Partners in Time (USA) rom, CRC32 885e88af
You can either use XdeltaUI or https://www.marcrobledo.com/RomPatcher.js/

Credits:
Creators of Yoshi Magic: Salanewt (Founder), Teawater/charleysdrpepper (Main Coder) 
Maker of this hack: SAIYAN48, with help from Teawater/charleysdrpepper and steve30avs