I’m not 100% sure I understand the 3 options but here’s my interpretation. Let me know if this isn’t what you intended.
- You just do every workout as scheduled but do it twice in the same day? So if you have 4x15min intervals you end up doing 8x15?
- Same as #1 but only on every other day
- Sub in SS workouts that focus on progressing interval lengths as opposed to number of intervals or workout length. So go from 4x15 to 2x30, for example.
#1 seems just insane to me haha. Doubling the HV plan will give you about 1000-1400 TSS/week. Most people would be absolutely fried from this very very quickly if their FTP is set even remotely close.
#2 seems more reasonable but because you are training for basically 8 150mi days in a row I would hesitate to do one-on one-off because you want to get used to how you do stacking long days back to back.
#3 seems like the best option to me. Check out the thread that I’ll link below for some premade workouts that extend the SS interval durations beyond what the stock workouts provide. And you can also download and use the workout creator to make your own custom workouts if what you’re looking for doesn’t already exist.