Try, and If you think better use a nylon screw, not a plastic.
From Cypress
http://www.cypress.com/file/136236/downloadGuidelines for Antenna Placement, Enclosure, and Ground Plane
? Always place the antenna in a corner of the PCB with sufficient clearance from the rest of the circuit.
? Always follow the antenna designer’s/manufacturer’s recommended ground pattern for the antenna. Commonly
used PCB antennas are variants of a monopole antenna. Monopole antennas need solid ground for proper
operation.
? Never place any component, planes, mounting screws, or traces in the antenna keep-out area across all layers.
The actual keep-out area depends on the antenna used.
? Do not place the antenna close to the plastic in the industrial design. Plastic has a higher dielectric constant than
air. Proximity of the plastic to the antenna results in the antenna’s seeing a higher effective dielectric constant.
This increases the electrical length of the antenna trace and reduces the resonant frequency.
? The battery cable or mic cable must not cross the antenna trace on the PCB on the same side of the antenna.
? The antenna must not be covered by a metallic enclosure completely. If the product has a metallic casing or a
shield, the casing must not cover the antenna. No metal is allowed in the antenna near-field.
? The orientation of the antenna should be in line with the final product orientation so that the radiation is
maximized in the desired direction.
? There must not be any ground directly below the antenna. See Figure 14.
? There must be enough ground at a distance (ground clearance) from the antenna and this ground plane must
have a minimum width. See Figure 10, Figure 15, and Figure 20.
? Plan to have a provision for an antenna matching network because a lot of parameters in the antenna’s proximity
(plastic, ground variation, substrate differences, and other components) can vary its impedance, and therefore,
the antenna may need retuning. If the impedance of the antenna is unknown, it is preferable to have a provision
for a PI or T network of three components, with 0 ohms populated in series components and no load for shunt
components. This helps you to populate any topology needed for a matching network later.
? When using the matching network values provided by the antenna manufacturer, ensure that you use the trace
length from the antenna to the matching network specified in the manufacturer datasheet or reference design.
? Always verify the antenna matching network with the final plastic enclosure in place and the product placed in
typical use case scenarios. For example, verify a mouse with its plastic held on the hand and placed on a mouse
pad, plastic, wood, metal, or floor.