I love the game, and can't wait for more. The concept is delightfully twisted, and the art and writing are great. Are you planning to revise the early text to reflect the added butt growth? Right now it's a little odd how it's not mentioned until Jane has practically doubled in width. Also, will she get more facial expressions at the larger sizes, or will it just be the one?
Lastly, if I might suggest a challenge modifier, or maybe just an element to include in the game somewhere: Have Jane's minimum silicone increase each time you max out, or as a consequence for something else. Anything to mess with her "base" size I think would be very fun :)