Engine Hatch Cover Release

[Zigzag03]

Duplicating a post I left on IRV2, I know a lot of folks read both forums but maybe will catch someone new who can help.

I'm probing the small hole in the rear of my engine hatch (pictured, sideways of course) with various size allen wrenches in hopes of catching the release. I've tried quite a few, including the 5/16 and 3/8 that have been suggested elsewhere. I crawled beneath, in hopes of being able to see what I'm trying to operate, to no avail. If I go straight in thru the hole, the wrench contacts something distinctly non-metallic. Below the hole there may be something, but I'm reluctant to tear the fabric further than the existing hole. Anyone have any insight for me and my old Chieftain? Thanks.