i am looking for a few answers on building a tumbler. 1. i am going to build an 8' tall drum but how wide should it be? 2. i was reading that it should turn at about 18-20 rpms. is this correct? 3. how course should the saw dust be to "break" the hides down for a soft tan? 4. do the thick hides have to be shaved thin for a soft tan or will leaving them in the tumbler longer break thru the thickness across the back. any info will be extremely helpful, thanks to whomever responds, gary r.