Just add this 3 linse at the top of your shBrushBash.js file. Since TWc activates plugins sorted by there name the core may be activated after your brush. The "Requires" info fixes this.
/*** |Requires|ShCore.js| ***/ -m -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to tiddlywiki+unsubscr...@googlegroups.com. To post to this group, send email to tiddlywiki@googlegroups.com. Visit this group at http://groups.google.com/group/tiddlywiki. For more options, visit https://groups.google.com/d/optout.