Hi Frank, welcome to FiberglassRV
No, I don't have any experience with rvcampercurtains.com
But, I've seen great curtains made out of everything from sheets to towels. Someone even (Legacy posts?) made curtains out of old jeans. So, I'd say it's whatever you wish to pay or whatever effort you want to put into making curtains.
Whatever you do, don't punch holes through the shell to add curtain rod brackets... there are better methods we can show you!