The fishing poles need to be light so the Addis brush is a compromise because the manuf dont have anything light for high work, but it does me for my domestic. We all have different requiements for what is a perfect brush, sounds like you want to clean Industrial work ? Oh the addis bristles clean with the sides when splayed, not with the tips.
8 jets, no problem. You match the number to the length of the brush, if you had a 3" brush you may only need one etc. I used a 6 jet on a 12" brush but went back to 4 as that was the optimum for me. If you go to 8 jets, the pressure will reduce so you may need smaller jets to get the water over/past the bristles. Also the T pieces take up much of the space on the broom head so you may need to trim the T junctions to get more in.
I dont carry 25 litres on my back, just 10L. Well under the army regulations yomping backback. By the way the standard backpack straps are useless they need really beeffing up otherwise the straps dig into your shoulders. I dont find the need for a waste belt but it would help many.
