Kathy,
I've done exactly that, mostly b/c I couldn't live w/o the Hardcores for a whole month! Also, this is my third time starting this rotation b/c I love the results so much!
Try this substitution (Thanks Jane for making this easier!)
Week One:
*Mon- Legs and Glutes then 20 minute run
Tues- Imax One (cardio intervals) SUB IMAX 3
Wed- Muscle Endurance (high rep, low-moderate weight) SUB MUSCLE MAX
Thurs- Pure Strength Legs and Abs, and run 20 minutes SUB GS LEGS AND CORE MAX
*Fri- Cardio and Weights SUB HSC
Sat- CTX Kickbox (cardio only) plus stability ball segment of Pyramid Upper Body SUB KM MINUS LEG DRILLS
Sun- Off
Week Two:
*Mon- Pyramid Lower Body plus 30 minutes Basic Step
Tues- Pyramid Upper Body plus 20 minutes run SUB 2 TIMESAVER PREMIXES FROM GS CHEST/TRI AND BBS PLUS AB ROUTINE
*Wed- Pyramid Lower Body plus 200 walking lunges SUB GS LEGS
Thurs- Imax 2 plus 10 minute Ab Hits
Fri- High Step Advanced plus 10 minutes Ab Hits SUB HSC/IMAX w/o FROM HC EXTREME Or just HSC
Sat- Kick, Punch and Crunch
Sun- Off
Week Three: THESE ARE HARDER TO FIND NEW SUBS FOR YOU COULD SUB LOMAX FOR MIC THOUGH. APPROX SAME CALORIE BURN, MUCH EASIER ON THE JOINTS AND INTERNAL ORGANS LOL!
*Mon- Legs and Glutes plus 20 minute run
Tues- Cardio kicks plus 10 minutes Ab Hits
Wed- Slow & Heavy Legs plus 200 walking lunges
*Thurs- Cross Train Express Upper Body plus Body Fusion
*Fri- Legs and Glutes plus 10 minutes Ab Hits
Sat- Maximum Intensity Cardio
Sun- Off
Week Four: COULD MAKE THE SAME SUBSTITUTIONS HERE AS IN PREVIOUS WEEKS, COULD SUB GS LEGS FOR ONE LEANER LEGS, AND THE GS UPPER BODIES FOR PUB REMBERING TO KEEP THE CORE WORK IN. I WOULD MAKE SOME SUBSTITUTIONS AND KEEP SOME THE SAME, THIS WILL GIVE YOUR WORKOUT THE GREATEST VARIETY AND KEEP YOUR MUSCLES SURPRISED!
Mon- Body Max (90 minute workout, first 20 minutes step, second 20 circuit, third 20 upper body endurance, 7 minute ABs, stretch)
Tues- Pyramid Upper Body plus 30 minutes Basic Step
Wed- Leaner Legs (high rep, medium-heavy weight)
Thur- Cross Train Express Cardio of choice plus Pyramid Lower Body stability ball segement only
Fri- Cross Train Express cardio of choice plus 10 minutes of Abs
Sat- Leaner Legs followed by Pyramid Lower Body stability ball segment only
Sun- Off