It's important that you marry the sluice to the dredge in the most efficient way. A sluice for a 6" or an 8" dredge needs to be designed for your particular application for best results. You may also want it to have gem recovery capability.
Depending on your pumps GPM output, and whether you are using a crash box or a flair and the types of overburden/gravels you will be running, has much to do with the sluice design. Such as.......
Riffle style, riffle height, riffle placement, how long the sluice box should be, how wide it should be, whether to go with an over under design, whether to make it a multi stage sluice or both, what type mat/mat's, whether to use punch plate, expanded metal, the angle of drop, etc.
If I were you, once you get the dredge specs and details, call
Heckler Fabricating and let them custom build a sluice to give you the best performance for your particular situation. Keene could do it but would cost way more. (either way it wont be cheap)
I'm with Alaskan Adventurer on the use of vortex mat. However I believe that you both would be better off using a modified Clarkson riffle setup instead of the Hungarian style, Read the report below and see why.
Sluice Design
Sounds like you are having the adventure of a lifetime and I wish you all the best!
GG~