fitting a new plastic bath?

shall i support the under side of the bath and the back with a 2 by 2 batten,as the kit supports legs dont look like it will take my 18 stone dead weight i think i can get a fixing with the bath in situ at the tap end as i plumbed this well back to the wall with flexi tap connections which allows me good access straight thru,then the back end which is the same again, and last, the side which is all easy to screw into the underside of the bath.also i want to fit a 2by2 frame to support the front of the bath also taking in mind the front cover panel your advice is appreciated as i want to do this way any way it looks a better way of installing im a panel beater by trade and a well capable of any diy but i am a bit slow, not slow but i do the job how i see it in the term so to speak, thanks mr f.