We have Southdowns, which are a similar Down breed. Provided any that need it are dagged until they're shorn we've found them no more susceptible to flystrike than the other breeds we've kept (Badger Face and Lleyn). About half our first-timers will have twins, then almost all have twins for several years before tending to have singles as they get older. They utilise grass very efficiently and eat probably 40% less grass and hay than our Badger Face. Depends what you mean by rougher ground - ours are on ancient meadow, so no high sugar Italian rye grass/white clover mix, and do very well. You're welcome to a copy of our Flock Plan, which includes the pre-lambing feeding regime we've found effective at producing healthy lambs, maintaining the ewe's condition score and supporting good milk yield.