Newby questions on HERMS

[herms bay]

I am starting a HERMS build and am using a 70/50/70 litre setup with 5500w elements in the HLT and Brew kettle. I am ok with electrics and control and am just seeing if there is any practical LFE out there that would help my Mech build. For instance; how high to put the element from the floor of brew kettle to aid whirlpool, pickup placement and whirlpool type and placement. wort recirculation methods (pipes or manifolds) etc.etc, just want to learn from everyone else's mistakes.
All advice before i drill holes greatly appreciated.