I haven’t seen the plans or the price, but generally my rule is that I can invest a few dollars in plans or classes or seminars on whatever topic and always learn something worth the money
If I learn one new thing, or save one mistake, or save a day of rebuilding something that didn’t work, I have long since paid for the cost of the education. I have hundreds of dollars of reference books (for example, a handbook on servo hydraulics at almost $200) where I learned one or two things that later on paid the cost of the book.
So I would buy any plans or cd’s easily before starting a project like that. sounds well worth it.
kcj