Use the importance nail extent. Your nails should just penetrate the Slate roof deck boards when setting them up. This is important since if the too long, they'll go right the way through the boards, breaking and splintering the wood at the back. This will lessen boards' thickness as well as typically power within the nails.
Vinyl siding is highly regarded as accessible many different sizes and sizes. It is relatively durable depending over the grade. You may need to stay out of "builders grade" as it not as durable many is probably the most inexpensive. However, all vinyl is inexpensive compared to other siding options and additionally maintenance free making it an attractive choice. Installation will run about $3 per square foot. The downside to vinyl is this many people feel will be looks "cheap" no matter how good the standard.