Which is correct, "summiting" or "summitting"?

This form of the word is not very common but does see some use as the present participle/gerund of "to summit" as in "Upon summit(t)ing the mountain we took photos but had to begin our descent immediately to make it down before dark".

Wiktionary only includes "summiting" but of course its publicly editable so no guarantees it's right.

Google suggests "summiting" as a correction when you search for "summitting" but there's not really many Google hits for either to be truly conclusive.

Google Ngram Viewer shows "summiting" in the lead recently...

... but "summitting" has the highest peak in the graph around about 1910 and was also in the lead from 1974 to 1980...

So I'm interested in whether any of the style guides, usage guides, or trusted English dictionaries such as OED or Websters Third have anything to say.

Solution 1:

Random house list it as summiting

verb (used without object)
7. to take part in a summit meeting.
8. to reach a summit: summited after a 14-hour climb.
verb (used with object)
9. to reach the summit of.

EDIT:
Tip: Use onelook.com to check multiple dictionaries.

Solution 2:

See benefited. Summited works by the same principle.