20 minute increments for one service, 15 minute increments for all others

Hi there,

We have a service ("Chakra Balancing") that is booked in 20 minute increments.

All other services are booked in 15-minute increments. (30 minutes, 45 minutes, etc.)

I tried to set this up using the admin interface, which is very rich, by setting the base increment to 5 — but that didn't work, perhaps because the programming doesn't account for such a small number.

What can I do to get this working the way we need?

Thanks,
Nabha