I would , even though I think that makes nelly bloom later .. Jackmani for sure ! It never hurts to do your own experiment and see whatgives you the results you are looking for ! :)

Hmm sorry I thought nelly was a early flower one . I always pruned my jackmanii and was happy with all the blooms. So disregard my post .

None of the really early flowering ones - old wood clems - are LFH's. They are all species, like armandii, montana, alpina, macropetala, etc. and are no prune clems (or prune immediately after bloom cycle). The large flowered hybrids - both early and late - are either heavy or light prune types but neither will produce flowers from low on the vine as they are flowering primarily on new growth so that means the terminal ends of the vining stems.

I (or mom nature) hard prune my Clematis and they bloom fully.

Doesn't really make any difference when or how hard you prune. Clems that flower on new growth (or mostly new growth) - like the two listed here - will have flowers produced at the terminal ends of that new growth. And that tends to be the top of the vines.