I've realised that marths spike this time around has a smaller hit box, I barely find myself spiking now-a-days.
But while I was facing my friend I accidently buffered a turn around and when I went to spike i was facing backwards. So then I noticed, the sword goes ALOT farther back, then it does forward. So when the sword is just about to complete the arc, THATS a reallly good time to connect the hit, because, it'll most likely spike. Its just a little tip, if it was found already, sorry 
But while I was facing my friend I accidently buffered a turn around and when I went to spike i was facing backwards. So then I noticed, the sword goes ALOT farther back, then it does forward. So when the sword is just about to complete the arc, THATS a reallly good time to connect the hit, because, it'll most likely spike. Its just a little tip, if it was found already, sorry