Personally Neva thought size of dog mattered for rabbits ,especially when shining at night,what I do know his size and bulk does lend a hand and those dark blustery stormy nights when strength and stamina come in to play,having got those extra pounds ,does help tremendous when constitution plays a big part,has the saying goes ,small light framed animals have a tendency to burn down so easily And need far more time on bed recovering to ready for next session.running from eleven till seven takes the right sort of animal and of course a good handler.atb bunnys.