Odd....I posted a reply before then when I logged back in, it was gone!

Oh well, all I said was Tarnee how does she respond to you just wrapping her arms (as in fold the wrap up so its a strip about 20cm wide, and wrap only her arms and torso).
Also you can buy extra large muslin wraps off ebay quite cheaply, and you can buy muslin by the metre at spotlight, maybe you can make some BIG wraps for her that way which will be cooler than a sheet.

Benjamin is currently down for his first sleep with an arm out...so far so good!