Stretched sprue us always too thin in the middle and too thick at the ends, but there are a couple sections on each pull that are usable. On a 24-30 inch pull, I can usually harvest a couple of usable sections 6-8 inches long from either side of the middle. Plenty usable in 1/72 and most 1/48 single seaters. You also get the advantage of being able to use noticeably thinner line for the control cables. You have to be ruthless in throwing out unusable pieces, otherwise you will be tempted to use them rather than stopping to make more once you get on a roll rigging.
sp