I am not sure if this will help, but being a fan of The Web, here is my tip if you are getting "rumbled". (for it 2 cents worth

)
I have yet to be rumbled with it and this could perhaps be to do with the load.
When puting your hand under the spectators and loading, I leave my hand there temporarily as i am showing there cards and slowly move the inside of my palm away first to ensure the plant is successful. This need a small amount of practice as to the spectator it should seem nothing has changed. keeping your hands over the spectators for the rest of the trick (as long as is possible) should prevent the spectator from turning their hand over before you want them to.
Doing it this way means the plant can be very light, and the feel of your fingers on the sides of their hands should cover the feeling of …well - you get the picture.
In summary :
a) don’t “push” the spider, just let it barely touch.
b) perform as much as possible over the spectators hands.
Hope this helps.
Mark