No problem, I only want to show that glider pilots are on the same team with other people demanding weather realism.
As for ops experience - in RL (with little oversimplification but good enough) air is heated not by the sun but by ground (ground is heated from the sun), this results in temp lapse rate - often visualized as skew-t diagrams - but in most times at some height - like those 4000feet or even higher there is temperature inversion - that is ambient air is hotter with height - and this effectively is a barrier for most thermals - as air cannot rise if surrounding air is less dense (hotter) - this is why in RL flying above inversion height is smooth rode and below it you have turbulence/thermals.
Btw if there is smog/dust in air this inversion height is quite visible as this dirty air is trapped by inversion (BTW there is a bug report about it as in msfs it is rendered as fog instead of layer).
Sometimes clouds are able to rise to significant inversion heigh and then they spill all over it to the sides - like the anvil of cumulonimbus clouds.
Generally setting single cu layer low should allow in msfs to fly above thermals as they should limit thermals height to cloud tops, Seb said about it in latest dev stream, but also noted that limit height is not accurate.