A few Hobie 18 facts...

The shroud anchor area -

This issue was from first production till early 80's. A stainless part was designed to distribute loads down the hull's side wall. This took loads directly off of the lip. This part (shroud anchor plate) has 4 bolts in an arch below the lip.

There have been no further problems at the rail area due to shroud anchor since that time.

Crossbar rail area -

Crossbar rail area racking issues began in 1984 when the company lowered the weight of the boat. The specific reason for cracking is that an inner reinforcement patch was narrowed (to reduce material usage / weight). The hulls were not fully bullet proof again until about 1989 when a larger inner patch was added in the post-glue stage (after the deck was glued on). This larger patch fully connected the deck to side walls inboard and outboard below the forward crossbar, from the inside. Earlier, a retrofit plate kit (same as the shroud anchor plates) was tried inboard and outboard of the front crossbar. This became standard in production followed by the patch in '89.

If you have an '84 to '89 hull (without the before mentioned patch and plates) I would suggest adding the internal patch and installing the crossbar plate kit. If you have wings... I would add a hatch in the transom /deck area and add the patches and plates there as well. This should protect the boat from the dreaded cross bar cracking issues.