I may be way off thinking it is a ground-effect issue, but try the following:
Get a lanc going at full speed, tuck in at 50 feet, stabilise the aircraft so that there is no stick input, and so that it cruises in that configuration for a minute or so. Then engage auto-level. The aircraft promptly climbs up to 200-250 feet.
Is this intentional? Is there a floor on the auto-level?
It does it whether combat trim is on or off.
K (who doesn't believe in altitude when it comes to flying a lanc =)