8 hour training plan, 4 days a week

With my work schedule, I have 4 days a week to train. I can’t train on work days. My days off each week change. Sometimes I have all 4 off in a row, then next week it’s every other day. I did a low volume plan last year, but it was hard keeping up some weeks. Due to being all taxing intervals, when I needed to do sessions back to back to back, my body didn’t have time to recover. The plan assumes you have every other day to complete the workouts.

I want to up my weekly ride hours up to about 8 per week this year. I think long easy rides really help me as well. I can do them and feel fine the next day. Polarized training seems to be what I want to do. But I can’t seem to make a plan. I tried the masters plan of 4 rides per week, but that still only gets me to approx 5.5 hours riding each week, which is what I do now. The other plan is 6 rides per week, which I can’t do.

So what should I do? Do I use the 4 days a week masters plan and just swap the workouts? Like for my first week it shows to do a 90 min endurance, 75 minute endurance, a 1 hour threshold, and another 75 minute interval session. Should I make my endurance sessions longer to get to 8 hours?Or do I adjust each workout to longer ones and sort of spread out the time? Do I try to keep the same tss every week as well?

It seems like the algorithm doesn’t want allow this type of plan and I’m not sure how to make it work.