Hi Mike,
You have to fix the luff first, i.e. the throat halyard needs to be tight. I assume that you mean the peak halyard when you mention the 'topping lift'. The PS, if rigged with gallows, doesn't usually have a topping lift. On my boat I do have a topping lift to hold the boom up when the sail is lowered, because I don't have gallows installed. I digress ...
I'd suggest taking the gallows off the boat, while you are setting up the mainsail:
The head should be snug (not really tight) on the gaff - no crease running along/under the gaff.
Throat and peak go up together, until the the luff is tight. The distance between the goose-neck and the cheek block has to accommodate the luff. The luff has to be tight before anything else. Then, when the peak halyard is pulled up, the leech will get tight and the sail will hold up the boom, but ...
if the foot (out-haul) is too loose, you will get a crease running from the peak to the tack, if the out-haul is too tight the crease runs from the throat to the clew.
(The out-haul and the peak halyard need to adjusted when you are sailing: in light winds the foot is slightly loose, in stronger winds the out-haul is tight to get a flatter sail. Whenever the the out-haul tension is changed, the peak will need to be set to get the crease out.)
Once the sail looks right (no big creases, foot slightly loose, ...), measure how high the gallows can be. Check that you can get the sail flat on the center-line using the main sheet. In a stronger wind the sail needs to be flat and the boom must not come to rest on the gallows when hardening up. Then check again with the main reefed down (first and second reef, one at the time).
Also, check the mast rake. It is easy to get more rake - I have a small block of wood behind the mast in the tabernacle -, but it is not that easy to reduce the rake. Obviously, too much rake will bring the end end of the boom down (a lot). Take the boat out for a sail or two ... then put the shortened gallows back onto the boat, or, install a topping lift instead
.
Cheers,
Peter