G'Day Stu,
I have several bags with cordura ears and prefer short to medim height ears. The height of the bag will depend on the depth of you butt (top to bottom) if it is shallow you will need a higher bag or a short bag with packing blocks for adjustment (probably a better idea as this will allow for uneven mounds).
Leather ears will get sticky if wet and the cordura ears treat them with a spray on food grade silicon lube to make them slipperier.
Go to a sand blaster and get NEW garnet sand for its extra weight. The old stuff will leak out the stitching. And remove any sling swivel studs from th butt or you will get un-explained vertical shots as the butt/stud rides between the ears and then down the back of the bag!
Cut the head off a case such as a 270 or a 30-06 to use as a funnel in the filler port of the bag.
hope this helps and yup Pete at Pro-Cal is a great help too!
Cheerio Ned