I have a rigid vang so I don't pay much attention to the lift. It is possible it was too tight for the reefed sail.
Then the obvious question is .... did you reset the rigid vang to get the aft end of the boom 'down', assuming you released the rigid vang when reefing?
The following may help (but may be a bit 'detailed') -
Based on normal sail design for almost all boats (but NOT for boats that are designed with significantly raked masts) ... the angle at the tack between the luff and foot (mast and boom) should be somewhere about 87-89°.
So, when setting up a topping lift (at the dock) and after you're SURE that the sail is 'raised correctly'**, measure the 'as raised' sail and validate that the tack angle is at least 90° (just use a square 'something' to measure that angle) ... and then PUT A MARK on your topping lift control line for full up. Ditto if using a rigid spring loaded vang. This will quickly 'eyeball' your mainsail to the 'basic' shape geometry that the sailmaker designed .......... and with the boom near centerline, the boat on a hard beat
- the area of the leech somewhere below the topmost batten 'should' be parallel
to the boat's centerline!
Then, accurately measure up from the tack to the first reefing tack .... and again, from the normal clew to the first
reefing clew. If the distance from the normal clew to the first reef clew is LESSER
than the distance from the normal tack to first reefing tack (first reef position carries the clew at a lesser tack angle) ...... put a second mark on your topping lift control or your rigid vang control - to be your 'eyeball' setting for how high the aft of the boom 'should' be initially. Do the same for all your 'reef' positions.
And then, when underway you 'tweak' (slightly loosen the topping lift control and slightly tighten the rigid vang control), etc. from this 'basic setting' to get all the (full set of) tell tales flowing correctly.
The amount of normal
'twist' will be set for 12-15kt. for a 'stock' plain vanilla sail even when reefed!!!!!!! Then, use the traveller and mainsheet tension for other amounts of desired 'twist'.
The result will be the 'as raised' shape of that sail will be 'real close' to how the sailmaker designed that sail.
** Dacron mainsails made before the year ~2000, and have a luff bolt rope in a sleeve, usually need to be stretched out along their luff via additional halyard tension by 1" extra 'stretch' for every 10-11 feet of luff length. Dacron mainsails made (for 'cruising purposes') after the year ~2000 usually will not require this luff 'stretch out'. Dacron mainsails, with bolt ropes, made for racing usually need this 1" per 10-11ft. of luff 'stretch out'.
Warning! - if you raise the dacron mainsail correctly, or put in a reef, usually the aft end of the boom will be parallel to the horizon or just a teeny bit higher than the gooseneck. If that aft end of the boom is lower
than the gooseneck end; then, the sail probably wasn't raised correctly (stretch out, etc.) or the sail needs some 'adjustment and 're-work' by a sail loft.
hope this helps.