I've been on these forums for quite a number of years now. This topic comes up two or three times a year it seems, mostly new folks to RVing, wanting the best for their set up. Always a good question.
The consensus on these forums has always been, "no" for all the reasons stated above. The biggest reason for no support under the slides is because of possible alignment problems, if the tires lost air, the ground softened under the main trailer supports and the trailer sunk in the ground, even very slightly, or any number of reasons the trailer could move, or settle (even a high wind would rock it.
With the supports under the slides, they will not move with the camper movement, causing stress on the slide mechanisms, and resulting in potential damage and bending.
Your camper slides are designed to be self-supporting from the camper body.
Now, you can support the entire camper, or block it, or do whatever, as long as it's on the main frames of the main body.