The default value of maple-minibuffer:parameters has left-fringe and right-fringe both set to 5, but the values are overridden by 0 when the frame is made:
https://github.com/honmaple/emacs-maple-minibuffer/blob/master/maple-minibuffer.el#L124
It would be ideal that any parameters defined in maple-minibuffer:parameters were honored in preference over the sensible defaults.