Just wanted to say that I think those are great things to try. Tip 352 is great for leaves. You can also try to gently pry open the narrow end of your rose tip a tiny bit to see if that helps.
I have always had a problem with the edges of my roses looking 'feathery'. I have tried stiffer icing, thinner icing, piping gel, opening my rose tip a little and I still get those edges!
But, you know, everyone always likes my roses. They ask how I get edges to look like that! I have finally decided to embrace my roses, smile and just say 'thank you' when I get a compliment.