the sinking tip weighted 7 was hard to push, like you need more arm strength.I am little hesitant to flex the rod with a great deal of arm stregth.
You can't 'push' a bamboo rod. You most likely have a rod that was made to cast a #5 DT line. Try that, s.l.o.w your cast down, and enjoy the wonders of casting.
Since the rod is unmarked, it may be as light as a 4wt, but I seriously doubt it's made for a 7 wt.
I have a 7 wt 2 pc with 2 matching tips that I built a number of years ago if you want a bamboo fly rod for bass fishing. Your purchase will serve you best for dry fly casting.