I've grooved hardwood shoot shafts and didn't see any improvements or advantage. Well seasoned shoots are more stable than quick dried ones. I like to give hardwood shoots a year to season and 2 is even better. After heat straightening I temper the shaft by starting at one end and heat and rotate the shoot moving down the shoot from end to end. This forces any excess moisture out so be careful of steam at the far end as you approach it. You may have to hand straighten while it's warm and lay it flat to cool completely. I've done this with sourwood, red osier, black haw viburnum and other dogwood shoots. They stay straighter than other shafts I have.