another recirculating biab question

I am finally at the end of my 4500 watt recirculating biab build .I have one more build question.
how much space do I need to leave between the element and my false bottom style bag support(it is a perforated ss sheet than has about 1 inch clearance all around it and 2 mm holes in it.I hope to recirculate and realise I need to be careful about emptying the slace below the false bottom.logically the smaller the space below the f/bottom the better but I wonder if too small an area causes more likely to scorch things,wort,grain ,bag??
thanks in advance
paul

IME - I have a slotted rack about 1" above the element that my bag rests on. I can recirculate with the valvue on my pump open about half way without issue (usually I keep it cracked open for a slow trickle, but I could open it up if I wanted to).

You may have more flow issues than me with the 2mm holes, but 1" clearance works for me.