Grar no you can't change the SLOT2 but you can change the moonshell one(Sorry I was in a rush I fail
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If its R4Menu by spinal,then read http://gbatemp.net/index.php?showtopic=236322
If it's the original R4 menu(and/or clones),then rename the .nds file* to _DS_MSHL.nds(or whatever your R4 uses as moonshell) and place it to wherever the original _DS_MSHL.nds is.
*homebrew only I think
BTW you might wanna use Wood,if you use the original,just saying.