Making stocks that fit well and look good takes time. Making stocks that work for you isn't usually all that hard. Once you have a working model, making it out of nice wood is easier.
Way back when, target shooters used to take a spare set of basic stocks and whittle, sand, add plastic wood, and repeat as needed until it seemed to fit their hand. Some started with whatever scrap wood was handy. Then they'd shoot it as is and adjust. This is where a Dremel and a sanding drum come into their own.
I don't know much about the SP101, but it looks like routing out for the spring housing wouldn't be hard. Making the wood-to-metal fit right is the hard part. My first gun project was making a replacement stock for a really cheap .22 revolver. I think Dad gave me that task as an aptitude test. I liked it!