I'd first look at how you have placed your hands on the handlebars. You need to have the pressure on your hands in the same places that you would if you doing pushups. Many people with hand numbness are compressing the nerves in their hands because of this. If you have placed your hands correctly, you *can* take considerable pressure on your hands with no numbness. It's not really how *much* weight you put on your hands but *where* on your hands you put it.
Get an anatomic diagram of the nerves in the hand and don't pressure these places. For example, don't hook your thumbs over the hoods where the pressure is on the web of your hand between your thumb and index finger. Don't hold the bars at the turn where it places pressure between the pads on the heel of your hand. Both of these are often done by new riders and they invariably lead to numbness.
In the photo below, the red arrows are the two places mentioned above. Similar issues can happen if you compress the nerves elsewhere on the hand. Notice how this is an issue between any two fingers for all intents and purposes.
I had spent years experimenting with bar tape, gloves, handlebars etc... to get rid of numbness. Then I took at look at the anatomy of the hand and the answer is obvious. Numbness instantly gone and has never returned.
