OK, as far as my experience with Bob and sub-q fluids goes... Bob and I are very familiar with them. I've been through 4 1000ml bags since May 10th or so.
At first, when Bob was just diagnosed DKA, I had to give him 2 100ml treatments a day, to rehydrate him. That was only for a couple days, then we cut back to 100ml a day. A few days later it went to every other day, then 3x a week, then 2x a week.
The original reason was to rehydrate. Once that was accomplished, the vet found that his potassium levels were too low. So, they added potassium to the 2nd bag, and I continued the sub-q fluids, not to rehydrate, but as a means to get the potassium into his system. This continued for a couple of months. It did help, and at one point he got up into the normal potassium range. Today he's a little below normal, which is why I've been looking into other ways to give him potassium. He and I just got tired of doing the "humpty-backed camel" thing when the primary reason for doing it was to give him potassium.
Alright, this is where I address the insulin absorption with fluids thing, and reveal Bob's dirty little secret... The question of "do fluids inhibit or aid the absorption of insulin" never applied to Bob. He was getting sub-q insulin in the scruff before the fluids treatment began. About a week. When my vet told me I was going to flood his scruff with fluids, she never told me to change sub-q locations of the insulin. Instead, she told me, and showed me how, to inject Bob's insulin inter-muscularly (IM shots). Her reasoning was that in doing so, the whole fluid and insulin question would be avoided. So for the final 9 weeks of his dance, he got BID injections of insulin into the big muscle (what we would call our hamstrings) in his back legs. I posted once in a "where do you shoot insulin?" thread that I did this. The 2 responses were "insulin is never shot that way", and "I can't believe a vet would tell you to do that" or words to that effect. At that point, I dropped out of the discussion. I was following vet orders, and I didn't want to argue about it, and it was working, which was the only thing that I cared about. That's the reason that you never saw any posts from me asking for dosing advice, or ever saw me create a SS. I didn't feel it would be worth the hassle to be told I was doing something "wrong", and have all the threads become a pros vs. cons thing. So I winged it.
One day, I'll post "Bob's Tail, A Case for IM Injections" in the Think Tank. All I know is that even if Bob was the only cat in history to get IM shots, it worked! Tomorrow he'll be off the juice for 2 months. I try not to advise others based on Bob. Most of the advise I give is based on what I have seen and read here, and from analyzing people's SS's. I do think I understand how PZI works, and I can examine someone's data and try to figure out what is going on and what will help, so that's what I try to focus on.
This I can tell you. I know that I shot pretty big doses (up to 3 units) into "non-shootable" numbers on a regular basis. And I know that Bob never displayed any hypo symptoms. The lowest I every tested his BG at was a 44, and I didn't flinch. All I did was keep an eye on him for a little while, then stopped worrying about it. I knew "what to do" if I needed to, but I never needed to. I also know that I would never tell someone else to dose that way.
I don't worry if you shoot a reduced dose into a low PS if I can see on your SS that kitty has not dropped severely before on that dose. But the huge difference is that your kitty isn't my kitty, and I realize that nobody worries more than a sugarcat's bean does because it's your cat, and it's right there in the same room as you are, and no matter what decision you make, it's you that has to live with it, not me. So I tend to be pretty conservative when it comes to dosing unless I see data that makes me not worry. In that case, I see my "job" as convincing you not to worry.
Bottom line - I am not qualified to tell you what the combination of sub-q fluids and sub-q insulin does to BG. I think it helps, but I've never done it.
whew. sort of glad to let Bob's secret out actually.
Carl