I have a Cigarette Bullet and I am adding external hydraulic steering. I have Hynautic 9” stroke cylinders and I am interested in the math/formulas that are needed to get them properly mounted or any tips/advice. Thanks!

Id reach out to Dustin Carter ( Carters power boats ) Broken Arrow OK, if you dont get your answer here, him and his father have restored many Cigs over the years

lots of information here, figure out what rams you have and what back cap....

https://imcosteering.com/imco-catalog-2022-v8.pdf

Also which hynautic rams?? some are for lower pressure systems....

I have the Hynautic K-5’s. I searched here on the board and they seem to be a popular choice with the DIY guys.

Can't provide any model specific advice, but generally speaking, there's a few items that apply to installing all ext steering systems:

1. Mount transom bracket for the ram/s on the same horizontal plane as the driveshaft or where the drive pivots up and down. I've seen them mounted a couple of inches higher (to clear the tabs) and owners report they work fine, but Imco wants them within 1 inch or so. This is supposed to prevent the rams from binding when drive trim is adjusted.

2. Probably most important, mock-up the install, before drilling any holes, to verify the steering rams run out of travel before the drive/s do.

3. Take a good look inside the bilge where the mounting holes need to be. Keep in mind there's also holes needed for the hyd hoses. If mounting the rams between the drives, you can most likely use a single dual ram mount. If installing the rams outboard of the drives, there will be 2 separate brackets and probably a couple more holes to drill.

4. When drilling thru the transom, do whatever you need to do that ensures the holes are straight. My ram brackets used a backing plate inside the bilge and there wasn't a lot of wiggle room where the 4 bolts came thru. I used the install as an excuse to buy a drill press. Picked up some scrap 1" thick aluminum to use as drill guides. When drilling the holes, probably best to use a 3/8" rechargeable drill. I started off with my 1/2" gear reduction drill and just abt broke my wrist when the bit dug in. Brad point drill bits work very nicely and leave a smooth clean hole. If you wanna go the extra mile, you can drill the bolt holes in the transom oversized, fill in the holes with resin/filler, then drill the holes in the resin to the correct size. This will help protect the wood around the holes if the sealant ever leaks.

Is this something you are going to piece together or is it a kit? Piecing it together will most likely costs more by the time you get all the misc hardware needed.
I bought a almost complete system from a member who was installing ext boxes and needed all new stuff. Was missing one oddball stud. Wound up having a machine shop make me a replacement to the tune of $85. Glad I wasn't missing any more hardware.