Installing a center drain shower pan where tub was. Old tub was elevated so trap and drain were above the floor (mobile home). I would rather not cut the floor under the shower to install the trap. Can I run about 25-30" of horizontal drain line (with 1/4"/foot angle) from shower drain and then put the trap in before before connecting to the vertical drain/vent where tub was connected? Also, this will be 2", not the tubs' 1 1/2" line. So, does the trap have to be right under the drain?

Thanks