Earlier in Piper, I had to hold the forward pressure to keep the nose down until 60kts ('air speed live') and at 70 kts take off.
Absolutely not!
Yes, hold the stick either all the way back, or at least effectively nose light, through the entire take off ground roll. PA-28's can be a little troublesome if forces off the ground too early, but any airplane would rather have the third wheel light during take off. The only exception to this are some T tailed aircraft (Tomahawk) which are better accelerated nose neutral.
Letting along the immense wear and loading being imposed on the nosewheel when it is forced down, you are setting yourself up for a wheelbarrow of the whole plane. If the mains come off before the nosewheel, the aircraft could groudloop around the nosewheel. If in doubt, search Youtube for "groundloop", and then imagine that happening to you at takeoff speed.
Every Cessna tricycle single I fly will start the takeoff with my holding the stick fully back, until the nose has come up noticeably, and then held there until it flies itself off. My technique will be similar in every other tricycle I fly, though maybe not full nose up stick held in, just enough to lighten the nose.
The notion of a rotate speed in a flight manual is a little "big airplane dreaming", during the writing. If the nose is held light, and at the right attitude, most planes will fly themselves off nicely when they are ready. The actual "rotate" is more to assure that by that speed, you are airborne (as there is not reason not to be - unless something is wrong!).
You fly the plane, it does not fly you!