This is the set-up I'm using for the cowl attachment. The plans call for a 1/4" overlap of the cowl on the fuselage. The overlap is actually about 1/2" on one side due to the built-in side thrust, but I was concerned that engine vibration transferred to the cowl by the nose ring would dislodge it. So I attached some 1/4"x1/2" stock at the edges of the firewall to provide more gluing surface. I also "rabbeted" the front of the nose so the cowl would install even with the fuselage sheeting.

I asked GW for suggestions on this and this is his reply. It would be useful for all of us, so here it is. Hope GW doesn't mind!

"Dave, I always attached mine with a cowl ring of sorts. 1/8" lite ply ring, just inside the cowl overlay area. The 1/4" stock you have applied will be fine. Once you get the cowl fitted and tacked in place. Tack it good!!.

Remove the engine, make a nice epoxy fillet around the inside of the cowl/firewall joint. Make sure to sand the glass good where it will be glued. Clean with alcohol after sanding the contact area. I'm sure you are using a Hyde mount, the side to side mass with a nose ring is minimal. Mainly rotational, very little actual pressure side to side. Make the nose ring a semi tight fit, with just enough play to slide the ring over the crankcase with some lube. It will wear quickly and find its own fit. GW "

Another builder suggested a fillet of fiberglass inside at the firewall/cowl joint.