Use a German gripper and a chain jack to put tension on the rope before attaching it to the cwt. It'll take you a couple times to feel it out but you'll be able to get pretty close the more you do it and at the end use a shortening block mark the cables that are the tightest or loosest and make the adjustments in shortening. It also helps if the shackles are the style with springs.

Thanks for the response. I'm not sure what a German gripper is?
Currently I use a choker and fist grips with a 3 ton hoist and pull to the counterweight. We get a lot of deflection though and it puts the tensions all over the place. I like the idea of using the shortening block and making those adjustments while shortening. That should help a lot.
Thanks!

Google, "coni-klam wire rope clamp"
Sorry "German grip" was the name it was introduced to me as, but no one out side of the local Otis branch here knows what it is lol. You can find one for 1/2 rope for about $800 but they are amazing. So fast to use and they don't crush the rope or make kinks. And they don't slip down the rope when you put them on like a traditional klein puller. If you do any high rise 2:1 running car style rope jobs you can pull the new rope so tight you only gain 1-2 or runby by the time you're done roping. Gets rid of that pucker factor cutting that last rope

wurtec sells them

What is best practice to help control the descent of the ropes as they are being replaced? I saw rope brake by wurtec. It has a lead time and is pricey. Will get it if that is the best option.

I guess it depends how you're doing it. But if you marry the ropes together and use the old rope to pull the new rope it's not bad at all