I highly encourage you to get the rays and breed them.
I have been trying to breed histrix for almost ten years now with no luck. I now have a group of five adult or sub-adult histrix and I am really trying.
I am pushing a ton of food at them and they are receiving 25% daily water changes. I am really hoping that by Spring I will have my first litter of these guys.
I really do not think that they are harder than other rays to breed. I think that they mature much more slowly than motoros do. My motoros have been kicking out a couple of litters per year for the past four years.
People that have not owned a histrix are really missing out. They are the most underrated ray in the hobby.
They will do very well for you in a 150.
Good luck,
Colin