We do it sometimes with just a few very well grown commercials, but use a small tup of a vigourous breed - we tried a Shetland last year, were very happy with the results and will use one of his half-bred sons this year - and, as others have said, give extra feed and care, and only allow hoggs to rear a single.
The only reason I would ever actively advocate it would be if you have a breed and ground where any uptupped ewe hoggs may become overfat if not bred. Which with Ryelands maybe could be an issue - but perhaps not on your ground in Wales, Sally?