How to convert a Laser to centre sheeting . note..it does take a little more effort to sheet in really hard so pointing really high is harder but it is more than made up or by the reduced capsizes and length of rope to pull in when going from reaching to hard on the wind.

Essentially take advantage of the  blocks (pulleys) on the boom and move them around.

Disassemble the block at the end of the boom and put it where the other block is. The halves may be joined by ordinary ss wood screws in the blocks and there are no ball bearings or anything flash so just unscrew and re-attach.(Some are all riveted. so see note below) Use the old middle block to build your new double deck strop style block setup.
The pictured tube over the securing rope is to keep the new block from catching in the ratchet block. The new strop you create is siliconed so some other user (or well meaning Learn To Sail or) will not dismantle your good work and say this is rubbish and try to re-rig in the old way.

The boom will not break (if not corroded and ancient) in half with a 4.7 rig and is probably OK even with radial and larger but you would probably need a "turbo vang" kit to pull it all down. This has only been tested in 20 knots with 4.7 and 80 kg sailors ...Boat becomes more modern style with vang (kicker) holding boom down and sheet controlling horizontal movement. It may even be legal to race as its all Laser parts

change block position. Just unscrew the screws ,change and refix. .. careful on the tightening its only plastic. Note. If your blocks are the riveted type leave the end one where it is. secure the rope tail to the boom Optimist style with a few hitches. You will have to get a pulley but the Clevco range are fine and about $15
make up strop using the old centre of the boom pulley. Any sort of tube will do just to put some stiffness in strop. Could use wire but not skin friendly or weave and knot a longer length of rope together to produce same bulk and stiffness.
attach to boat.
finished... rigged just like you do if transom style
Strop detail ..Classic loop so ends run together and can be pushed down tube. Loop big enough so if you want to remove pulley in future it's easy. Silicon gun down tube and pull through. Put a figure 8 at the other end of tube to help it all stay together if you don't do the silicon. WHILE THIS HAS BEEN TESTED IT HAS NOT BEEN DONE TO DESTRUCTION SO ALL YOUR OWN RISK>THE RATCHET FIXING STRENGTH IS UNKNOWN BUT GIVEN LOADS IT USED TO TAKE BEFORE TURBO VANGS AND WITH FULL SIZED MAINS IT SHOULD BE FINE. ...while purchase in new config doesn't give the same pull power it is adequate to 20 knots by which time dry land is a good choice.