If you are in aero position you want the hips to be more 'over' the pedals/bottom bracket.
You could buy a dedicated TT-bike for that (including aero frametubes and all that) or, like a decent chunck of triathletes, aero your bike as much as possible. That includes a tt-seatpost to move the saddle forward.

I had my measurements taken and I know how to make my normal bike fit me for a triathlon. It includes swapping the saddle, mounting aerobars, lowering the cockpit, etc. etc. It works for me and my goal during a triathlon is (apart from finishing in a decent time ) overtaking at least 1 'rea' timetrial bike, and as much carbon bikes as I can.
Me being on a 'normal' touring/race bike (alu fuji sportif 2.3), or on a steel, vintage, 80's bike.
You have to pick your battles though...

Good luck!