I'm on the other side of the pond, but 'size wise' I would say that mine are not the largest of 'large fowl' compared with my huge Brahmas, but are way bigger than my 'large fowl' Naked Necks. The La Fleche roosters I have are slim alert looking birds. The hens are more rounded, and both sexes weigh heavier than you would expect. The last rooster my husband 'culled' (I am not in to killing) weighed 7.5 lbs and was not yet fully grow, if this is any good indicator.
My roosters don't ever seem to be aggressive, but a recent one has taken over as alpha male from a huge Brahma.
When crossed with other breeds, they seem to grow very quickly.
The roo pictured above by mjgigax from the article by Kycklingar has very 'pink' ear lobes and I think (and am ready to be corrected!) that this is a breed fault and they should be nicely white. My roos have good clear white ear lobes and good 'horns', but I have some 'non-black' feathers coming in with some of them, which i'm sure is another undesirable trait. Oh well, maybe someday I'll get a really good one!