In August 2021 I heard from Kenneth who had improved the cooling on his t610.
Very effective mod using two 12v filament printer cooling fans (40mm x 40mm x 10mm) powered by the 4 pin 12v jack located at the bottom of the motherboard. Available on eBay for about $2.00 US each.
Hot glued two of the fans side by side and attached them to case cover using two small electrical ties. Small shims about 2mm thick glued to fan face provides clearance so that the fan doesn't scrub against metal case.
Fans are very silent and keep the cpu and case very cool. Fans pull air from the outside of the case and push it up towards the CPU.
Points of note:
Kenneth has picked suitably small fans (40mm x 40mm x 10mm) to fit the available space.
These are radial fans. They draw air in in the usual fashion but blow it out at right-angles through a vent on one side of the fan. You need to make sure that when you fit them you orientate the fans correctly so the airflow is directed at the CPU heatsink.
These fans seem to be associated with 3D/extrusion printers. I found a reasonable eBay search term to be "40mm 10mm fan radial 12V".
The ones on ebay.uk are closer to £5 each or £3 if you buy four. Beware: As is often the case the odd listing says 'radial' but the photos are of 'axial' fans. (I normally go by the photos if there is a conflict).
Whilst Kenneth is using 12V fans he is actually running them from a 5V supply. Under running the fans helps keep things silent whilst using two fans boosts the amount of air being circulated to compensate.
Any comments? email me. Added August 2021