Extract Super high gravity

So I normally do allgrain, but im in the mood to play around with some small 1 or 2 gallon extract batches of fun stuff. looking to work towards that 20% abv mark, with extract I've read everything on yeast and the process of re-adding concentrated wort as fermentation slows. So process isnt my question.

If starting with all extract i would have problems getting the attenuation i want, so what ratio do you think extact to sugar would help dry it out.

Some reading that I've done I found out that Muntons extracts attenuates more than Breiss extracts... Perhaps you wouldn't need to add any sugar with Muntons.

I haven't gone over 30% sugar, but at that high an ABV, you could probably go 50%. Consider shooting for 15% and adjusting once the first fermentation is done.

Check out Brewing Network's Brew Strong Archives. 5/30/10 & 6/13/10 are "High Gravity Brewing" part I & II. It's 2 hours of great tips. (Like feeding the sugar in steps starting just after high krausen. . .)