If your looking for honest feedback & your so confident in your product why not bring some along to the Brisbane stackers get together on the 18th. I'm sure you'll get all the honesty you can handle face to face & you can save yourself the $10.00 advertising fee.
^^^ There is no reason to ridicule and mock someone for stacking bitumen mate. That would be like mocking those whom buy and sell iron and steel. Though not 'precious', still plenty of wealth to be earned in it. I reckon the original poster is better off trading with Local Council workers.
Please don't bring any to the meet, we don't want to be exposed to any toxic chemicals that bismuth has.