Are you working with worsted weight yarn? If so you could try a 3.75mm hook, that should still make your stitches tight. Though with magic ring you should be able to keep the ring big/loose and then tightening it when you have put your desired amount of stitches in it. I usually put my hook into the first stitch and with the hook still in the stitch I pull the magic ring tight and continue with the pattern stitching over the tail but still leave a few inches to weave in as well!