Dear Declan
I enjoy reading your essay, it is clear and well written. It is surprising to me that you have considered similar ideas as some other participants. You argue that there is an energy field. According to my work, I would conceive your field as some sort of aether and therefore as some sort of preferred system of reference. In my work I argue that no experiment can rule out the possibility of a preferred frame of reference and therefore the aether idea could be maintained. I discuss the variability of the speed of light both in my entry and in my essay. Einstein knew in 1911 that the speed of light was not really constant. The formula that you found for the frequency as function of the gravitational potential is the same formula he found. Some other participants like James Putnam also developed a similar line of thought as yours. I hope you could take a look at our works.
Good luck in the contest
Israel