Oh well, it will be good practice for me - and there will be some practice at fixing up bad sewing later, I can already see some places where it will be necessary - and I'm not pulling it back that far now.
The other thing I didn't really think through was that a black and white line drawing isn't really a good final cartoon. I am having to make up the shading as I go. This is because I am using two photos of the house, taken years apart, from different angles.
So far there has been a bit of pulling out but not too much. However, it will be one of those things where you do what you think is right and then put in other bits which change how it looks. (Some colour theory here, which I am researching for another project.) Unlike painting, I can't go over it to change it. I either live with it or take it out. And that's not easy because of all the bits that overlap! So living with it seems to be the option, let's hope it is not too disappointing.