I use a Melin AMG-808-E 1/4" wide by 1/4" shank. The overall length is 4 inches. So when I use that bit I push the bit all the way up in the router and move it back down about a 1/4". The reason is the bit is very long and just seating the bit to the length of the collet tends to make the bit run out of round. When you start the router and it sounds funny then stop and reseat the bit and try again. Also be aware that the overall bit length is 4 inches so depending on your clamping setup the bit will be closer to the spoil board during rapid movements so make sure you wont hit any clamps.
I have cut a lot of 1.5" treated pine and 1.5" glued up maple plywood with it. The bit works fine but because the bit is so long you can get vibration in the project and make clamps come loose. So I found out the hard way that I should have screwed down a project just a few nights ago. The material came up in the back while cutting and ruined the project.
The bits works but there are some caveats that you have to address to use such a long bit.
I got the Melin AMG-808-E from zoro.com. Sure you can get it else where.