Mon: Remember I'm the guy who keeps failing to execute the plan and race properly, so take this with a pinch of salt...
P&D have 8k to 15k tune-up races before the LSR on weeks =-2/-4/-6. These could be xc races (but might be too late in the season).
You could drop the mid week Lactate runs in weeks -17 to -7 and replace them with a saturday xc (but again, as you say, it will probably be too much for the sunday MP chunk long runs in weeks -16, -13 and -9). Plus I am assuming your xc race pace is similar to your lactate threshold pace...
Or you shift the long runs to some day in the week...monday morning 5am? Ouch. Treadmill 20 miler Wednesday after work? mmmmm....