Your understanding (your first paragraph) is correct, and this is what the equations say as well (when they\'re entered correctly, and nothing is throwing a fit).
The power generated with efficient generator setups is enough to power cloak up to substantial ship sizes, but as you increase mass (e.g. block count), you have to dedicate more and more of the blocks to power generation, until you finally reach the point at which it becomes impossible to maintain permacloak+radar jamming because energy regen efficiency has gotten too low (because of the decreasing efficiency of the main curve, and the 25 e/sec being the only thing powering additional power generators that are added), and then the point at which it becomes impossible to maintain permacloak alone. You can maintain radar jamming up to some rather large block counts, however.
If the math is accurate, it looks like 1,333,333 e/sec is the hard limit for permacloaking (100 e/sec/block), the point at which above which it becomes impossible to cloak even a ship composed of 100% power generators, regardless of how they are arranged or how long they are (or the point at which, if a ship core\'s mass has to be cloaked too).
For reference, the equation I solved (for n) is epb=((1/(1+1.00069^-((x/3)^1.7005*n*0.333))-0.5)*2*1000000 + 25 * (x-2)*n) / ((x-2)*n). Entering any x (I tested 600 and 3000 even though 3000 would be a 1000m-in-every-direction power generator), and 100 for epb, resulted in a value for n, which I then put back into ((1/(1+1.00069^-((x/3)^1.7005*n*0.333))-0.5)*2*1000000 + 25 * (x-2)*n) to get a value for the actual e/sec, which was 1.33333e6 (1,333,333 e/sec) with both x=600 and x=3000.
For epb=150 (cloaking+radar jamming), I get 1,200,000 e/sec as the hard limit.