bottom line thread is used in bobbins all the time- and 60 wt just means you won't have to change the bobbin so often (it will hold more :)
people use all kinds of different combinations- invisible thread on top- bobbin wt on bottom- the same top & bottom-
silk in the top-
if it works for you and is a good thread- that doesn't break all the time- use it.
if you find you have all kinds of problems with it- then switch one or the other and try again.