The only sensible route is to test your maxes and use those numbers as your maxes.
The second, less sensible route, is to work up to a heavy double or triple and guess what your maxes are.
The third route (and this is nearing nonsensical) is to take your old pre-injury numbers and subtract a reasonable guesstimate percentage from them. Say 10-20%. and use that as a working max for a time.
Why are you doing this "MEBB" progression in the first place?