As i described it in "Bigger Fleets" , u go into Data Folder / English and Edit the "Techtree.xml" . There u can change how much + points each Research give. Example
Basic Min - Defaul 5
Change it to 15 and once u researched it ingame, u got a + of 15. Its not a percent number. Percent numbers are just in raceconfig.xml as it seems.