Trying to maintain rank while switching back & forth from sitewide 301 to 302 redirects?

[WhiteCap]

My company's website has earned industry "authority" over the years and ranks well for a number of keywords. For reasons not worth explaining, we've moved the entire site (all pages) to be secured (https from http). When we launch our completely new website in 5 months from now, we will launch it as "http:" For the next 5 months, we're stuck with using site-wide "https". Is it better to 301 or 302 all pages (from http -> https), with the intent to move back to 301 in 5 months from now? Obviously, this situation is not ideal, but we'd like to preserve as much authority/presence as possible. What should we do and why? Any input would be greatly appreciated!