Notice a real difference in myself running CJC/Ipa alongside Reta compared to Tirz solo. Building muscle steadily now, and even though it's gradual, the visual changes reinforce my sense that this combination is paying off.
Back when I stuck with just Tirz while hitting the gym and cycling, the weight came off fast, but I couldn't see any muscle gains at all, and honestly felt like I was actively losing muscle mass, weaker pushing through max effort or high reps at the gym. Fatigue set in noticeably quicker too. Added creatine to my supplement routine roughly six months back as well, which should help with recovery and short intense bursts for maxing out.
Been running CJC/Ipa for around seven months now, following a five-days-on, two-off cycle stretched across twelve weeks on, four weeks off. Due for a break soon actually.
Everybody's different though, and dosing needs shift person to person, so expect your outcome to differ quite a bit from mine.