Reposting as the original was accidentally deleted: 

First things first: Welcome to the community! It's always nice to see people taking their first steps into content creation. If you have not already, make sure you have your account settings configured to give you email updates for reviews and whatever else you'd like. Also, under "account info" you can "view your statistics" to manage your stories and see how many favorites you have (favorites do not give notifications, but people who have favorited your story will receive email notifications whenever they are updated). Finally, it seems you are already paying close attention to scale and I appreciate that immensely. There is an imperfect instrument under "writing tools" called the "giantess converter" that you may find useful, but it seems like you already seem to have the calculations down. Oh, and as this is a repost, I'll also add that the two "delete" buttons on reviews are bugged and only delete the original review rather than the response. XD

I already saw this story being updated on GTSCity and I know GW isn't quite caught up yet. I haven't been reading the story on GC because I'm not a huge fan of the website's format for reading longer stories, but I think I'll pop over there to read ahead now! Don't be afraid to edit for word choice and make little tweaks to the story as you upload to GW, however. While I don't see any issues with the story so far, I know from experience that my first forays into writing were a little messy at first. While your readers may not always pick up on your mistakes/missed opportunities, I don't see any harm in improving your story as you improve your writing skills. To reiterate, though: I don't see any issues at the moment. This is just a general principle from someone who just started writing five months ago.

Now for the story itself: I have only read these two chapters so far and have not read ahead on GC as of the time of posting, but this story really scratches an itch for me. For one thing, I appreciate that you're actually taking time to develop your characters and not just jumping into the action and sizey shenanigans. So far, the story is pretty wholesome and I love the gentle vibe. On top of that, you seem to be playing close attention to scale, which I adore as both a size enthusiast and a math nerd. It's something I always take great care to do with my own writing and I wish more authors did as well. In terms of your execution: I don't really have any notes yet. Your dialogue is solid, albeit somewhat sparse. Your verb tense is consistent, though it does always strike me as a little odd when people use past-tense verbs to describe a story that is occurring in the present alongside active-tense verbs (not a flaw with your writing, just one of my broader nitpicks with the English language).

I like how you've introduced rules for the portals and you even preempted one of my own questions when you showed how reversing the sequence of the portals can cause shrinking. One thing I may have overlooked, but I assume the portals grow/shrink with each use along with the object? Otherwise, I imagine the object would eventually get too big to pass through the portal in the case of an infinite growth loop, thus getting stuck between the portals. I imagine the portals will shrink proportionately as well. Maybe this happens in a later chapter, though.

Finally, a few preemptive notes: I like the images. They are well-integrated in the story and don't distract me at all. They are an excellent visual aid. I am wary of including images in my own writing because I prefer to let people imagine my characters, but these are well-done and only enhance the experience for me. Some writers/artists will probably give you shit for using AI because creatives often have an irrational prejudice against AI, but just ignore them. As far as I can tell, you're doing all of the writing yourself and the images just supplement the story.

You may also start receiving requests from people to put their personal interests in the story. I'd advise against this. While fanservice is nice and all, the only thing motivating the events of the story should be the motivations of your characters and yourself. It's great when people are passionate enough to make suggestions and if it fits within the frame of your characters and scope of your plot, I don't see the harm in indulging them every now and then. But it's your story and you shouldn't derail it to please/appease anyone else.

P.S. I have yet to implement any images in my story, but I do have one short story coming out soon that was inspired by a collage, which I may include to pay homage to the artist. Do you have any tricks/tips for formatting images on this site before I try it for myself? Like I said earlier, I think it was very well done here.