One (not exactly awesome, I admit) possibility to express the general idea behind it.

I often find that with headings and titles, a good approach is to translate the section in question, and *then* decide what the title should be. What is the thrust of your text here? How would *you* entitle it if you were writing it directly in English? This is especially true with idomatic headings (like all those ones based on "xxx peut en cacher un autre"!). You may want to include one or two of the key notions from the idiom in question (in your case, some reference to either 'less' or 'more' might be appropriate), but (in this case) the heading (probably) really only serves to attract interest, to make sure that people read the text; it (probably) doesn't contain any actual "information" for the target readership, as such, so you can be a bit free with it, IMHO.

this is the most accurate idiom I know for this expression; Maybe it would be better to change the order: in for a pound, in for a penny. Good Luck!
http://www.usingenglish.com/reference/idioms/in-for-a-penny,...

... in the Agency's view a more detailed legal examination of the legislation, including
the principle of "he who can do the most can also do the least", leads to ...
www.itst.dk/static/publikationer-uk/annual_report_2002/bila...

He who can do the most can also do the least. [English]. Senator Nolin: Honourable
senators, does the Leader of the Government think the group in front of ...
www.parl.gc.ca/37/2/parlbus/chambus/senate/deb-e/066db_2003...

... an application to our field of the legal precept that ‘he who can do the most can do the least’, ...
eseries.ipa.org.uk/prev/newsletter/98-1/castro.htm -

He who can do the most can do the least.
lugansky.homestead.com/files/Concert_13_01_00.htm

This is a French proverb with the meaning that someone who can perform and difficult or complicated task can all the more be expected to perform an easy or simple task. I don't know of any phrase or proverb in English with a similar meaning. I would suggest coming up with a new title, based on the content of the section, as someone else suggested.

Although it's not a very current phrase as I don't believe we really use an equivalent in English, I feel like "if you can move mountains, you can move molehills" is definitely the closest, clearest translation for this.