I usually use Didier Rosada's articles on preferments as a guide on matters like this and, on that basis, the maximum amount of poolish is 80% of the formula water. See, for example, Rosada's article here:http://web.archive.org/web/20040814193817/cafemeetingplace.com/archives/food3_apr2004.htm
Whether 80% poolish is likely to get you into trouble is something you may have to tell us. Remember, also, that you have to use the correct amount of yeast for the poolish as discussed in the above article.
There is also a companion Rosada article here:http://web.archive.org/web/20050829015510/www.cafemeetingplace.com/archives/food4_dec2004.htm
Unfortunately, the Rosada articles, which were retrieved from archives, do not show the photos of the break point. Norma found another version of the article with some photos, at http://www.bakerconnection.com/artisanbaker/article_04.htm
, but, as can be seen, the photos do not show much detail.