element thickness

I am designing yagi for 910 Mhz.
I designed yagi using freeware program quickyagi(qy4) and i
am trying to simulate it using nec2 (4nec2).

what i found using simulation is "Decreasing element thickness increasing gain"
Is this correct ?

To increase gain, if i go on reduce thickness, will that have any other impact ?

What's the optimal element thickness for UHF (800Mhz-1Ghz) Yagi ?

(about my design: 4 element yagi, 915 Mhz, element diameter = 4mm )

Regards.

The thickness of Yagi?s elements affects the beamwidth of the antenna and indirectly the gain (narrow beamdwidth increase the gain).

Gain Factor (dBi) = 41000 / [Beamwidth Elevation (deg) * Beamwidth Azimuth (deg)]

The beamwidth is affected by the length, diameter, and spacing of all the individual elements.

The thickness of the driven element (which is a dipole) affects the frequency bandwidth of the antenna. For wide frequency bandwidths sometimes the driven element is a folded dipole.

Only a simulator can give you the right optimization for the thickness of these elements.