Okay, tested this on my Boot2 4.1E Wii with Hackmii installer v2.
Started wii, when SM loaded, I inserted SD, clicked the SD icon, asked to load boot.elf, clicked yes.
Wiimod loaded up fine. Then went to apps/bootmii-casper/boot.elf, and it kicked me back to the SM.
The same happened with cboot2-casper, just kicked me back to the SM.
When the Wii is off and the SD inserted, I started the wii and it loaded straight to wiimod.
Hope I've helped and not hindered lol.