Funny you mentioned it BM
we had 3 foal crops from Three Solid Bars and 1 foal crop from Tru Blu Texan, who still has more body and bone than Arnold. Arnold is NOT a heavy muscled stallion, on the contrary he is rather elegant in comparison to your tipical quarter horse type, due to a 50% influx of TB breeding.
We never had any problems with breeding our stallions to maiden mares on a large scale. 3 of our maidens foaled on their own without our help this year. In many cases when we are present at birth we pull a foal out, there is no point in sitting and watching the birth when it could be over and done with much easier and quicker for the mare.
But the most horrific foaling of our 2 maiden mares was by our little 14'2 cutting stallion Metallic Oak when we nearly lost the mares and foals. Simply because cutting horses are born with more body bulk on the width of their shoulders and they get more chances of getting stuck in a birth canal of a maiden mare. Short Quarter Horses usually carry more bulk than tall ones.
cheers, lena