Arm warmers? Actually mine are pretty lightweight and they can stuff anywhere. The shell....why did have to bring the damn shell up? That shell is occasionally homeless though it easily goes in the phone pocket. It's Pearl Izumi Elite and crunches up reasonably small but then sorta grows. May to September I suffer the fates which usually means an occasional soaked though drenching. Winter months means shell wearing most of the time though swing days (fall & spring) I tie it around my waist. Ok my crazy idea on shells is to pack an appropriately sized garbage bag (white) with precut head & arm holes. But until I go sub 165 pounds I'll carry the shell, the damned shell.