My question relates to the Antenova M20057. In my application I require the PCB, which the antenna will be mounted on, to be in direct contact with a Aluminium cylinder. This violates the requirement of no ground or tracks to be placed below the antenna, as this cylinder will be on the bottom of the PCB with the antenna on the top. It is possible to offset the antenna so it isn't centered, however this then decreases the ground planes on either side. Offsetting the antenna will increase the distance between it and the Aluminium cylinder.
My question relates to the trade-off between the two. Would the performance of the antenna be worse off centered (but very close to a metallic object ~0.8mm, PCB thickness) or offset (~10mm from the edge of the PCB, but ~1.9mm - ~3mm off the metallic object)?