Apex should be consistent, ball speed should increase 5mph per club as you go up thru the bag.
You may not have the swing speed to get any more out of a longer iron.
Lay the grass on a bed of modified type 1 (Type 1 with the fines removed) the professional 3g/4g have shredded rubber tyres to give some protection and a bit of sand brushed thru but doubt you will be using the quality they use.
Ideally you want a good level and proper base layer. Do it once...
I was on the course, my girlfriend was there for the walk. I accidentally hit the ball and it flew up her bum.
Took her to the Hospital, doctor examined her and said "That's up a fairway"