I ran a 60'' rear finish mower behind my little YM1110, it worked but barely. So a YM1500, should be no problem, but you may need to put some weight on the front of your tractor to counter balance the mower.
I do have suitcase weights on the front.I went to Howse web site and for a 5' finish mower suggested hp is 20-35,I read where Yanmar YM1500 is 17hp,If I take it easy will it be fine?