I don’t think I’d go quite that low. I’d probably do a third, maybe half depending on what it looked like when I started clipping

That's my inclination as well. But I am not a rose grower, just learning. Also I will admit it's a crappy picture, which makes it hard to tell what's what.

Thanks.

Westerland is a climber so don't prune the main canes. These are the ones coming directly from the ground. Instead cut back the lateral canes (the side ones coming from the main cane) to just a few inches. If possible, training the main canes horizontally will cause more branches to form and more flowers.

I did a bit of side branch pruning, but your comment gave me an idea. I'm going plant another climber about 8 feet away with a similar triangular support and build a lattice work bridge between them so I can train each to go laterally across to each other. In 3 years it will look lovely. Thanks.