I have been shooting Beman ICS 340s out of my '03 Patriot SC for close to a year now with good results. I have only had one crack during that time frame and that was more my fault than the arrows themselves. Total arrow weight with a 100 grain head, 3, 4 inch plastic AAE vanes and with the shaft cut to approximately 30.25 inches is 430 grains. That same shaft with a 75 grain point and at 28.5 inch length with 3, 3 inch vanes would probably be in the 375-380 range. The size 400s might do the trick as they are lighter per inch and since your arrow are going to be about 2 inches shorter than mine, with possibly a lighter tip weight, then the weaker spine of the 400s might be right on the money.

According to Bow Jackson's website, www.bowjackson.com, the size 400s with a 75 grain point cut to a 28.5 inch length and with 3, 2 7/8 inch plastic vanes would be approximately 367 grains. By switching that to 3 inch feathers you would be down at approximately 354 grains.

Hope this helps.