You say that the power plug is 5.5x2.1 but on the lightningasic website the mass of chinese text against the picture of the power cables ends with the number 2.5mm I would guess this is the power plug size?

Also the cable you show 8 into one does not look suitable, as it would need to carry 30 amps through the single plug to the power supply and I think that is way over the spec for those.