just a note here ,if you were to make a 8' footer ,you would need alot more water flow , otherwise the crap,will just collect further down,where pressure drops,you say in mich, were theres lots of dirt and little gold,then in my opinion you would want as much flow as you can get otherwise you will build up a lot of crap,with little gold ,frequent cleanups without the payoff for your time and effort,gold regardless of mich, or where your at is heavier than anything else in that stream,i would suggest classifing down as much is reasonable for you,this would alow you to (sluice) more gold bearing matieral,and would allow you to get away with less water flow, because you would be washing smaller matieral ,having said that ,you still need a good bit of water flow to clear the sluice of crap, gold will drop out , dont be affraid of flow ,the more the better. these guys on here know their stuff,they will steer you right. good luck man!