My draw weight is 70 lbs and draw length is 27.5". I'm hunting elk this year and was running low on 340 spine arrows, so I went to my bow shop to get more. They talked me into using my 400 spine arrows instead of my 340's since I have more of those already on hand. According to several of them, I'm at the very edge of where 400 spine is usable as long as I don't add any more weight to them. At least 3 of them claimed that they also run 400's at 70 lbs and it works fine. However that contradicts every spine chart I've seen. Per their recommendation I went ahead and shot my 400 spine arrows for a bit and they appeared to fly just fine. Very straight and fast at 288 fps based on their chrono. The carbon to carbon length is between 27 1/8" to 27 1/4" . Im calculating that they weigh ~386 grains with the blazer vanes and 100 grain point as opposed to the 340's with 50 grain insert weighing 350 grains. Just curious if other people have ran 400 spine at this poundage and draw length successfully or had spine issues?