I have done some reading about this and suggest you at least look into the high performance panels. Following is a snippet of info.
VIP technology is available that uses aerogel as a core material. Aerogel is a powdery silica based material which has an R value of around 9 per inch at atmospheric pressure. Glacier Bay, Inc., uses this core material in BARRIER ULTRA-R super insulation panels. BARRIER ULTRA-R panels have an R value of 50 per inch. They come with a 25 year performance warranty against loss in R value. This is possible because the aerogel core chemically adsorbs gas molecules that pass through the vacuum barrier membrane. This getter activity allows the panel to maintain its high vacuum level and R value over an extended time.
Marine-refrigeration ice-boxes built with BARRIER ULTRA-R have a total wall thickness of about two and one quarter inches. Although the initial cost of this material is higher than other insulation options, it is often chosen for new marine-refrigeration construction and marine-refrigeration ice-box retrofit projects because usable space can potentially be doubled or more for a given external volume. When coupled with the long performance life and superior energy performance, it may offer the greatest value.
ain't what ya do, it's the way that ya do it...