Vero 29 V2.0 temp droop chart
If the ambient temp in the tent is is approx 25C (77F), when the COBs are driven soft (~25W) we might be able to achieve a Tj of 30C (TC ~27C) and almost no temp droop whatsoever. Run at medium power (~50W),
Tj 50-60C (Tc 35-40C) is a fair target range and still no significant loss of efficiency.
Run mid-hard (70-100W) or run with somewhat insufficient cooling could lead to a Tj of 100C (Tc 60-70C) with a temp droop of less than 10%. Not ideal but should still have very good output. May experience some lumen depreciation over time at these temps.
The Optic Lighting Vero 29 200W lamp tested about 3% temp droop, running each Vero29 2.0 at 2.15A (80W). I measured TC 40-45C. They did not go overboard with cooling but achieved it efficiently using CPU cooler style and running low RPM fans at 12V. So I think any COB should be able to come in at or under 4% temp droop without too much trouble.