Yet another arrow conundrum

[Hoosierarcher88]

For the most part all of my bows i have owned with the exception of one have been easily tuneable with my 400 spine carbons and 300 grain tips. Now in steps my new bow and i have absolutely no clue where to start on arrows. My new bow is a 40# great northern bushbow which with my drawlength will put me at 38# otf. The weakest arrow shaft i own is .400 spine so i know new shafts are on the menu for her. Does anybody who has expirience with these bushbows have a suggestion as to a decent starting point and with that being said, do you guys feel 520-540 grains will be too much for arrow weight?

[Orion]

Probably a 600 spine if you want to cut them about an inch longer than your draw length (which I'm assuming is about 27 inches, thus 28-inch shafts) and load the front end.  If you builg a 520-540 grain arrow you'll be at 13/-14 gpp.  That's pretty much. They'll probably fly OK, but will drop off fast, even at 20 yards from that light a bow. 

[blacktailbob]

I'm shooting 41# but at 30" draw, so I'm that affects a lot.
400s were a bit too stiff and piling on weight made them drop like rocks past 20 yds.
Found some 32" 450 spine to start with figuring I could cut them as I went. Turns out they shoot great no matter weather it's 100 grain or 200 tips at full length. With 125s it puts the arrows right 10 gpp and still fast with acceptable noise.

[Hoosierarcher88]

Probably a 600 spine if you want to cut them about an inch longer than your draw length (which I'm assuming is about 27 inches, thus 28-inch shafts) and load the front end.  If you builg a 520-540 grain arrow you'll be at 13/-14 gpp.  That's pretty much. They'll probably fly OK, but will drop off fast, even at 20 yards from that light a bow.

that is what im kinda worried about. I normally shoot around 650-720 grains but that is from 55# bows. This is my first venture into low draw weight longbows

[Hoosierarcher88]

Im kind of leaning towards 1716 aluminums with 125 grain tips. Spine calculator show pretty much spot on and puts me just at or above 10 grain per pound