Hi mate,1 or 2 brake rotors will do the job. About 5-10 kilo of anything heavy really.the heavier the better so your pots don't drag.

 I've got 20 kilos in my pot but it is pro size and it still floats down really slowly when it's dry. Doesn't seem to move off its mark though. 

cheers. will be pulling by hand, so may try 10kg first and see how i go.

 I pull mine by hand I'm pretty knackered by the 4th pot my son is a big help. 

 I use steel base pots and I have used countersunk screws to fix pine slats to the underneath of the steel base perimeter to stop the steel scratching /gouging the side of the boat.  3 seasons so far and they are still in good nick. 

Paul

 Hey mate, I make jarrah base/pine batten pots. 2 x 5kg plates is perfect, though you really can use any old steel provided it is heavy for its size and doesnt take up too much room. IMO something else to consider too, especially with timber base pots is to ensure that, besides a good strong jarrah frame and obviously pine battens that are strong enough, the amout of wood used in the construction of the pot should be kept to a minimum so as to reduce water drag. There's a lot of weird ass looking pots on facebook etc that are gonna go on more walks than a spolit dog.

 But that all changes when you drop them in. Weight in them out of water is obviously down to the amount of water a wooden bottomed pot will soak up. Put that water, back in the water, it weighs zero. Best way I can explain it. We used to run some deckie-killer wooden bottoms, pot weighed about 75kg wet. But they wouldn't hold nearly as well in a swell as a steel bottom with 20kg of ballast weighing in at 45-50kg. The dimensions of steel used in the bottom matter, too--Square section bar used as the bottom runners weighs in at almost double (or half as much again?, i'll look it up). what the round bar, same dimension, weighs.

Brody's mention of wooden runners on steel bottoms has been used in the industry for many years, although, IMO, not that widely. The idea was not boat protection, but noise on the bottom. Some fishermen feel that steel bottoms scrape and make a noise the crays don't like. If they are heavy enough, they won't move, and won't scrape. But wooden bottoms did seem to outfish steel bottoms, on certain types of ground, certain times of the year. 

Thanks for the tips guys!