Great look at what’s under the pad .... But a few suggestions....1) Use fresh marine caulk...and not one that has been sitting around the house for a year and comes out in clumps because it has far exceeded its useful life.
2) Don't mix any caulk and contact cement...if you are going to let excessive caulk ooze out around the plate clean up the excess and let it set before putting the contact cement on. 3) It is called contact cement for a reason....never apply contact cement to only one surface...it is applied to both surfaces (hull and underside of pad), kept the two surfaces separated till the glue tacks up and you can touch it with your finger without the glue pulling away from the surface. Then carefully join the two surfaces from the still attached edge with a roller or squeegee until the entire surface makes contact. You only get one shot...once the two surfaces make contact there is no moving or adjusting them...at this point you are finished...go sailing...there is no need to put weight on anything... if you screwed up and miss aligned the pad or got air bubbles you can break down the contact cement with a number of solvents and start all over again...check that the solvent you choose doesn't eat up/melt the plastic hull material...the best way is to do it right the first time.

Again great look at what is going on under the pad...