What ever the plan dimensions are, scale them up or down to suit the pump you have or intend to have.
If you only want to drag around a 6kg 2T pump, then don't make your sluice part 16" wide... The pump just wouldn't deliver enough water.
Also you can adjust the size according to the materials you have scrounged up.
There is no one rule on what sizes you need to use - at the end of the day , you're just using a hopper with water blasting in it to break up any clay & wash your rocks, then everything slides over a classifier to do it's job. Anything small falls thru & goes down your sluice section. There you put in what ever you prefer.
Mother nature wasn't fussy when rivers were created & they got all sorts of obstructions, rocks, logs, crevices etc. that all catch gold & trap it there - bit the same with a sluice.
Be it riffles, ribbed matting, carpet, Honeycomb rubber door matting, security door grid, expanded metal or the whole thing intirely made of wood, plastic or metal.
The thing is though again dependant on the water you can put thru it. A smaller pump will need a smaller sluice with smaller riffles etc. You want enough water to allow your riffles to clear the lights you put thru
There's no hope of my 1" pump running my river sluice I built.
I tried, but even at a steep angle, water just gently flows over the riffles that are clogged up & gravels build up in front of them too. No good.
You'll want to have your pump running in normal conditions at no more than half throttle so you allways have a little more in reserve should you need more flow or pressure.
4stroke pumps are quieter, uses less fuel but do weigh a bit more.
Also decide on the kinds of areas you want to use the HB in.
Will you need to carry your gear a long way or will you park your car next to the spot?
if you can park next to the river then there's no probs using a big 2" 6HP pump.
Some people make their HB's so the whole lot ban be carted around on a trolley.
Mine will be on a cargo backpack
