Tweaking Cary SLP-98P F1 Preamp

As you know for SLP-98, the F1 mod is a significant improvement over the standard. I just bought one used and the stock 6SN7 tubes that come with it are horrible. So, I am waiting for WE6SN7 tubes for it. Until it arrives I want to ask people with experience with F1. I have Pass X350.5 amp driving Soundlab ESL speakers.

1. How good can it get with best tubes?
2. Some have recommended using NOS 6f8g/adapter instead of 6SN7, any thoughts?
3. After getting the best tubes, is it still worth it to direct-couple it? It is supposed to improve bass, dynamics....
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I’ve been amazed by the improvements I have gained through using Symposium Rollerblock Jr’s under my VAC tube preamp. I think the Cary preamp will benefit as well speaking as a former SLP-98P owner (not F1). My Cary came across a bit lush and lacking a bit of detail and air. The Rollerblocks really improve these aspects.
Do you put them under the preamp's feet or under the chassis?
How do Rollerblock Jr compared to something EVP blocks for isolation?