My house was built in 1952. There is no plywood underneath the aluminum siding, only this fiberboard looking stuff. When I gutted the inside of my house I was able to touch some of this stuff and it didn't seem too sturdy... at least nowhere near as strong as plywood.

When installing new vinyl siding is there anything I need to keep in mind when working with this material?

Never installed vinyl siding in it, but did aluminum. Had to make sure nailed in studs. That fiber board has no holding power.

Good luck

Chuck