Acrylic warps both from heat and from absorption of water more on one side than the other. I believe even 1/4 inch thick acrylic will warp badly eventually. Are you planning on removing the black plastic strip that goes across, front to back, to reduce bowing out of the glass front and back? You can't expect to silicone acrylic to glass and use that as a replacement for the black strip. Even the silicone made to be used with acrylic doesn't adhere well enough to acrylic to let it be used that way.