Wood – Table saw blade width

There is NO problem with using an 8 inch dado blade on a 10 inch saw. In fact, it is quite common to do so. I use an 8 inch stack on my Delta contractor's saw with no problems, and before that, I used an 8 inch wobble dado.

You certainly would not want to use a 12 inch blade on a 10 inch saw, as that large of a blade might have clearance problems as it is adjusted. Use of a larger blade also causes somewhat larger tip speeds, so that might potentially cause problems. (Unlikely, but possible, since the differential in tip speed would be only 20%.) Perhaps these issues are what the author meant when they made that statement.

In going to a smaller blade diameter though, the only question is whether that blade will be able to reach the surface of your table. On an 8 inch blade there is no problem.

Could you do it... Yes. There are a few problems with this setup.

First, if the saw does not have a locking trigger how will you turn it on when you are cutting? If it does have a locking trigger, you'll want a way to turn the tool on/off quickly and easily. This could be achieved by connecting the saw to a power strip, and mounting the strip in an easily accessible area. You'd then use the switch on the power strip to turn the saw on/off.

Will mounting the saw make changing the blade difficult/impossible?

Mounting a jigsaw in this way could make it easier to force the wood, which could lead to binding, flexing, and even cause the blade to break (which could be deadly).

Lastly, why are you using a jigsaw for long straight cuts? Long straight cuts are far easier with a table/circular saw. The great thing about a jigsaw, is that the blade can bend and flex slightly. This makes cutting contours easier, but will make long straight cuts more difficult.