splits and checks

Hi all,brand new to this forum so forgive me if this has been answered a 1000 times,i;ve been having major dramas losing timber to splitting,checking and cracks...........green timber i know moves/shrinks alot but i;ve slabbed timber that;s been down 25yrs with same results.All timber i use gets the ends sealed straight after cutting and stored in dark,dry spot in my shed...i;m running about 80% losses atm......is there a product similar to pentacryl we can get in oz??? btw i work with mainly salmon gum and scrubby cypress but at this rate it would;nt matter,please guy;s any advise..........rory70.