Stage builder method cant use SDHC cards, so thats out.
This leaves you with a couple of options:
'Homebrew method' (though ive heard recently this may not work for sdhc cards, but i was almost positive it did) which is launching pm with a brawl disc using the homebrew launcher.
Letterbomb Method: Basically 'halfway to installing homwbrew' - letterbomb lets you launch without installing homebrew to your console, but esentially running the app from your sd card.
or
USB loading: - useful if you dont have an ntsc brawl. loading an iso from a usb stick with PM on the sd card. requires installinh homebrew, usbloader apps, cios's.
Pick your poison, its all rather easy. you may have issues one way and prefer to try the other