I've always shot cedar from my traditional bows, but just ordered a dozen carbons for my 50# Robertson longbow. I used the spine calculator and ended up getting Carbon X Piledriver 250's at 30". They'll be three fletched with 5.5" feathers and have 125grn steel inserts/145grn Stos broadheads for a total of 270 on the front.
You think I did okay? (I like heavy. :) )
Our bows are like good dogs and will do whatever we ask of them without whining, but I believe most longbows, and Robertsons for sure, are happier shooting wood.
Well...I've got plenty of that! I reckon I'll find out.
I have long bows and they seem to be pretty happy shooting carbon, I know I'm happy shooting them. the only way I lose an arrow is if I miss and can't find it, can't remember the last time I broke one, usually just wear out the feathers and stick new ones on.
I also think that wood arrows are very cool also but unless your using sinew for bow string and tying on your feathers and cutting your arrow nocks into the arrow and doing some flint knapping etc. whats the difference.
I find the nice thing about shooting carbons is I don't have to go too heavy on the front if I don't want to, but also, can if I want to.
Sounds to me like you might be shooting a heavier spined arrow than you really have to, I shoot about the same weight as you and I shoot GT1535's and GT 3555's but that is what is cool about carbon, load the front up and get it shooting.