Don't make it so hard. This is the way to do this.

For the bench and monolift length figure the length of the bar you will use and leave room off each side for spotting and loading. I personally would not go less than 10 foot.

The mono will be sitting on rubber mats or plywood or both. These are 4x6 or 4x8. So you have 4 in length.

Monolift - 4 x 10

For the bench you will need two pieces of rubber of plywood side by side so 8 foot.

Bench - 8 x 10

Don't go by the footprint - this is a huge mistake everyone makes with these and racks. Go by the space that will be needed with the barbell and your own body (some bench with feet out in front on them - thus longer than the bench itself).

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Dave Tate