Large Support Trestles Under Construction

When I have to lift something large or heavy, I usually lift it in stages, support each stage with a different height support.   Depending on how heavy or bulky, I use various things I have around the house or shop.   In the fall of 2020 I was installing a Mini Split AC in the shop, and neede to raise the Condenser/Compressor unit about 50&quo; high.   Well I didn't want to try it by myself and there wasn't anybody around who could help, so I started thinking about lift stages.  
I already had 4 of the 6-1/4" high support trestles, but I neede to raise it higher, so I considered building two more, taller trestles..      

Using two standard support trestles to hold each end of the outside unit.

Close look at two suuport trestles stacked.   These are my old standard trestles, each has a 1/2" peg at the top on opposite corners and a 12" hole in the bottom to match the pegs.   The pegs make sure one trestle doesn't slide off the one below.