I have UATs for my RAM500 FACET and Cougar. Both have flamed out at one time or another due to retained air in the UAT despite conscientious effort to be sure all air is excluded from the UAT before flight (eg inverting, tapping, shaking with turbine running-not always an easy procedure). It is a pain to try to get all the air out of a UAT, particularly as I frequently open the fuel system and shift the turbine between the two aircraft. The UAT is also a pain because it is best mounted upright and is only available in one size with only one size tubing connectors (5 mm polyurethane). It does serve as an additional 'final filter'

I am using the felt clunk supplied by JHH and Wren with my MW44-Sabre. Seems to work well permitting almost all fuel to be emptied before bubbles. However, the (Tygon) fuel tubing I use stiffens up in kero over time, and does not let the Felt clunk move around inside the tank as well as I would like. I know BVM used to have a thinner walled more flexible tank clunk tubing. Does anyone know its specs and where one could get a yard or so?