If you ever need to disable the “ctrl shift f5″ option from site studio sites then just create a component that appends to the ss_layout_head_info, javascript that removes the keypress event:

IDOC

<$include super.ss_layout_head_info$>

.
Javascript

		//unregister keypress events if users not contributor or admin
		if (SSContributorMode.IS_COMPATIBLE_IE_ENVIRONMENT) {
			document.detachEvent('onkeydown', SSContributorMode.KeyCommandHandler)
		} else if (SSContributorMode.IS_COMPATIBLE_FF_ENVIRONMENT) {
			document.removeEventListener('keypress', SSContributorMode.KeyCommandHandler, false);
		}

I`ve used this in the past to only allow contributors the ability to go into contributor mode by wrapping the javascript in a small idoc user security check.