Although I have made bows from ERC,I haven't made any style of lever bow with it. But I've made about every kinda lever bow you can think of with quite a bit of different species of wood. If I were to try making one from ERC I would def back the working limbs only with sinew and either rawhide back the whole thing over that or just rawhide over the levers cus even tho the levers are stiff they are still under strain and it would protect them from the stresses and from getting dinged up cus its such a soft wood. Exact dimensions depends upon what length of bow,your draw weight,your draw length,what exact style of lever bow,stiff handle or bendy,and the ratio of lever to working limbs. If you can answer me those questions I can prob come up with a good starting point and game plan for ya.