FATMAP difficulty grade
Most easily accessed from Thredbo from skinning North for about a kilometre from the top of Merritt's, then another 2 km North East and you will end up near the top of the Southern Twin Valley, from here the Southern Valley provides some nice snow quality lower down (away from the exposed wind scoured areas) and some nice pitches.
It doesn't hold many of the consistent fall lines which the Northern Twin Valley does.
The area flattens out around halfway depending on which line you take, as there are plenty, but the snow deteriorates following this flatter area, a base of around a metre at Spencer's Creek is a good indication for decent conditions lower down into the valley.
Take care when the spring melt comes, there are plenty of streams underneath, and the vegetation is thick.
Otherwise, in good fresh conditions, this area is simply awesome, visit the northern valley too! Hike/skin back up the way you came to return.