On arriving at the entrance to Raheenleagh Forest at
you will be confronted by security fences and signs giving notice of wind turbine construction, off-limits to the public.
However, I could imagine a scenario whereby you might choose to hop over a ditch adjacent to the barriers, and furtively walk up the forest track, hoping to avoid security personnel.
Using your GPS, you might then use those forest tracks to exit the forestry on its western edge and emerge onto open hillside.
There would (most likely) ensue a squelchy ascent, initially through clumps of gorse, until you reached the saddle with Croghan Kinsella. Google Map's Satellite View would suggest continuing over the saddle for a short distance, over a fence, and then climbing a gate on your right.
You'd walk on this track for a few minutes before taking a left turn which quickly brings you to the summit area.
You'd probably walk around the rough ground to the left of the track for a bit, attempting to ascertain the summit, but you might well decide that the highest point was the ditch to the left of the track.
Most likely, you'll retrace your steps, hoping to evade detection as you pass the construction works.
But I couldn't say for sure. I drove straight home. Linkback: https://mountainviews.ie/summit/1432/comment/18431/