Thanks for the replies !!!
but, correct me If Im wrong!!!
I always love the humbuckers mounted directly in the body, so, If I need to put some foam, or more foam to raise them, does it affect the tone???
will be better to put a small piece of wood ?
I appreciatte your opinions on this case!!
For the most part, no, I don't think so.
You could use wood, but you'd have to cut it perfectly, and also cut a channel for the wires to to through, and I'm sure there are other intricacies that I'm overlooking at the moment.
Plus the fact that you're stuck with that height, and over time wood expands/shrinks and if your string height changes, or any number of things that can/will change over the years, you'll be cutting new wood blocks a couple, or a few, more times over the life of the guitar.
The sound of the wood resonating doesn't get transferred to the pickups through the pickup itself. Pickups don't produce sound by vibrating themselves, it's the disruption of the magnetic field, and 99.99% of that disruption comes from the vibrating string(s).
What direct mount does is give you a few 'advantages' (this is speculative),
The p/ups don't move or vibrate on a set of springs, giving a more 'solid foundation' for your tone since the p/ups don't move in relationship to the strings.
No mounting rings. Less parts to come loose/alter tone. Plus the neck p/up can be set a little closer to the neck (the bridge can be closer to the bridge as well) without the rings and this DOES alter tone slightly.
No pickgaurd. Most guitars with pickguards are front mounted, and the extra routing can alter the tone of the wood, and some people just don't like pickguards for the appearance.
After all that, let me answer your question.
I don't think you'll notice any difference in tone if you use foam or if you use a fitted block of wood. Either way the p/ups are solidly mounted to the wood and aren't going to vibrate much, if any, differently. (not that this is going to effect the tone to a noticeable degree even if it does vibrate).