Thanks all for the quick responses. I use 1/4 plywood for the panels. I cut the groove using two passes over the table saw to get the right width of groove for the plywood. I'll try priming the panel before I assemble to see if that helps and easing the edge slightly.

Your advice is much appreciated.

In a pinch You can also shoot a 5/8" pin behind the panel between the frame and panel, this will push the panel forward.

I never had a complaint about it.

MDF is not cheap cardboard. We have found it to be the perfect mtl. for paint grade doors. 1 piece paint doesn't crack at rail and style joint. Doesn't shrinking and swelling during seasonal changes. doesn't bridge at panel to rail and style intersection. Prep time is zero. Takes paint wonderfully. The biggest problem we have with products like this is we have been telling customers that these products are garbage for so long that we now believe it. During the downturn years 2009 -2013 we got into doing restoration "water damage" and got quite the education. MDF and particle board heal up just as good as plywood and lumber. These two products were engineered for the cabinet industry.

It's a learning curve to spray so that doesn't happen. In your case I'd calk the joint so the paint makes a smooth transition between panel and style. We would do this after the first primer coat. Re-prime and then top coat. We do pre-prime the panels before assembly. Next time experiment with spraying just enough so it is covered but no so much the paint puddles at the style panel joint.

Chris, please post your website love seeing other people's work.

Pure garbage MDF and Particleboard that's the tune if your small and want to stay in business most small guys can't compete with a 2 shift 50 person shop pumping out particle board cabinets all-day. So you have to be special unique if I had the money I would hire Dave before he kicks off his work will be worth a lot after hes gone. We have to say were artist period and artists only use the best material.

1/4" ply is not 1/4" . Size your plows to fit w h at they are selling you. A n f plea a e stay away from MDF. You cannot compete with the cheep boys so you should be using the best of materials and working the top of the market.
My opinion, alone

You can specify what they call true 1/4" .

Thanks again. Lots of good suggestions. I'd like to stay with a plywood panel if possible. I'll try pre-priming the panel before assemble and keep my groove as tight as possible. I have put together some doors to try some of the suggestions in the thread.

Much appreciated.

We've produced 1000s of doors with MDF panels
We find it superior for paint grade
It's dimensionally stable, flatter, doesn't telegraph grain thru the finish, and adds some weight to the door
My supplier offers raw mdf, mdf core veneered panels in 1/4" and 5.2mm and veneer core plywood in 5.2mm in certain species
I usually order veneered panels on mdf core when possible with matching veneer or mill option back for the same reason as above.
You can order your cutters with 5.2mm if you want to stay with the inferior plywood or 1/4" if you're using true 1/4 panels

Split adjustable groover from Freeborn.