those staves are not too short at all.
60" is 150 cm. If the wood is not dry I would start by cutting it to 5x5 cm pieces (2x2 inches) and let it season for a while until it's dry. when drying the propeller can also be forced out. strap it so a board and leave it there to dry.
If the wood is already dry, I would start with the 60" piece. They seem quite wide BTW. how wide are they? if over 6 cm then you can get 2 bows out of one stave!
My dimensions would be 1,5 cm wide tips and then a handle of 3 cm for example. then the thickness: if the handle is 3 cm wide then the handle would be good to be 3-3.5 cm thick at first. the thickness should also taper some towards the tips.
you can also make the bow wider, for example 3,5 cm. if so then the handle should be at least as thick as wide if you want it to bend through.
then just start to bend it nice and slow. I would aim for 55# at that lenght. so if you go for 55# never pull more. and then just start to take off some wood so that it comes around nicely.
If the wood is dry the propeller can be forced out some by a heat gun and clamps. (NEVER HEAT THE BACK OF THE BOW). only the belly. or then it can be steamed. One easy option is putting it in water for a week or so, and then press it ti form. thus there is no such rush as in these other procedures. then of course it takes more time to dry again..
hope this helped.