Skywatcher Finder Bracket - Plunger Thread Size?

[Pinpoint]

Does anyone here know what the size of thread is for the hole into which the spring loaded plunger screws? I lengthened the stalk on my finder bracket to avoid the end of the telescope dew shield occulting part of the finder FoV and now need to replace the plunger with an actual screw in order to achieve a firm alignment between finder and scope.

Thanks for looking, any info muchly appreciated

Pete

[Bizibilder]

M8 x 0.75 metric "fine" series.