Training for sleeping on the tummy

Mummy was trying to train Ian to sleep on his tummy but under estimated his arms strength, he could support himself on his arms and took a long time before he could settle down for 1 hr sleep only...but he prefer not to have his legs straighten...look at the odd position in the picture He looks like he is sleeping pretty soundly isn't he?? well mummy will keep on trying...since it's said that he will sleep better on tummy...dunno if it's true