Expanding 250 RO

[maple flats]

I am expanding my 2 membrane 4x40 RO to 4 membrane. Plan to try running all 4 in series, the 1st 2 are in series. While I realize I won't double the permeate removal I hope to gain at least 50% removal. I've had a spare set of 4x40 membranes for several years and I recently bought 2 300 PSI 4x40 vessels is SS. My rig is a Ray Gingerich converted to electric. Those who have made their own, what do they call the parts to mount the vessel? One is a cradle of sorts and then a SS band circles the vessel and the band has a T head bolt on each end which is tightened around the vessel and it clamps the vessel to the cradel and the steel frame behind it. I see pictures of these but have not found a listing to buy them. Please advise.
'm expecting it to remove more permeat so I can go higher than 2% to 8% in one pass. I plan to first try the same pump and it will thus still be a 250 GPH but I am hoping to get to 11-12% on a single pass, still running at about 275 PSI.

[maple flats]

After talking with Ray Gingerich about expanding my EZ 250 Deer Run RO, it looks like my best option is not to expand it, but to make another 250. Without the right pump anything I add to expand my existing 250 will not gain enough if any gain and the pump needed for a 500 GPH RO is far more than what is needed for a 250 dollar wise.
Ray suggested I build a new 250 and use 1 if I only have an average sap day and run both when I need more RO. I will be planning what I need to do to make another RO. It appears the new one will be wall mounted and have it's own heater to prevent freezing. I have the 2 membranes and SS canisters good for 300 PSI. I'll figure out what else I need and go from there. I definately need a HP pump to move at least 5 gpm @ 300 PSI, wash tank, flow meters and the valves,fittings, gauges, needle valves, shut offs etc. I think I'll use an electric low pressure feed pump and an electric hi pressure pump. For the low one I think I'll use the same one I have to feed my flue pan washer, It's a 1 HP SS 1"pressure booster pump, it gets 70-80 PSI.
Where do you guys find the other items?