Esco cantilever/stylus mods for Zu Denon 103R

ESCCo are in the UK, Soundsmith the USA. This consideration as much as anything will swing most people's choice.
Where ESCCo may score over Soundsmith is the fact they provide diamond tips from scratch ie a more bespoke service, whereas Soundsmith provide from stock.
My ESCCo Zu 103 is still playing the role of giant killer, blowing my Orpheus out of the water.
BUT, I am a BIG fan of Peter Lederman at Soundsmith, and am actively considering his Straingauge to go up against the Zu 103. We shall see (hear).

I'm very curious about Soundsmith vs. Expert for the mod. I'm heard a lot about Expert from Lencoheaven, but mostly from European users. So is it any better than Soundsmith? IMO Soundsmith does great work. Could Expert be any better?

Suspect it's all in the same ball park. Soundsmith and ESCCo both have long and distinguished histories. They both have great feedback. I get the impression the actual diamond tips are more bespoke with ESCCo, but beyond this I can't help.
All I can say is, that for the price, the end result is fantastic, and the quality of work/customer service exemplary. Let's hear from some happy Soundsmith retipped customers.
Can't wait to compare to the Straingauge.

This hobby is bad for OCD! Small adjustments to VTF/VTA/azimuth are all making differences to the sound. Luckily it's all positive with VTF esp. making real improvements. Still finding closer to 2.5 makes more sense than the ESCCo advised 2.0.
Will be auditioning the Straingauge, but this cart is so persuasive that the demo will really have to blow me away or present such a persuasively different perspective on the music to sway me.

I've used modified Denon 103R's for the better part of 5-6 years now, the most recent versions being one in an ebony body that has been retipped (and potted, as Zu does with theirs) by Soundsmith with their $250 retip (ruby cantilever and line contact stylus) and currently a 103R in an aluminum body, also potted and retipped by Soundsmith with their midline $250 retip.

While I found the stock conical on the 103R to sound best right around 2.6 grams VTF, I can dial back the retipped versions I have to around 2.450 to 2.475 (yes, it will be that sensitive to VTF when it fully breaks in and you get into those zones). Going below that in terms of VTF the cartridge becomes very "airy" and detailed but loses the drive, slam and top to bottom coherency that the 103 series is really famous for and excels at with an improved body. Lower VTF may give you more "audiophile" qualities but will sound less like real music IMO. If I had to track mine below 2.45 I would probably look for another cartridge. Based on my experience, you are on the right track between 2.45 and 2.5 for VTF.

I would expect the paratrace to be very similar to Soundsmith's $350 retip. That would mean that it should be a detail champ but will also be extremely fussy on setup as you are finding out. But get it locked in and you will be rewarded.

FWIW, even Soundsmith's $250 line contact retip is a ton more sensitive to proper setup (alignment, azimuth, VTF/SRA) than the stock conical stylus on the 103 series.