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Ok, after a bit more spreadsheet wrangling I think I have this one figured out. For 35% more airflow at the same hz (larger maf), you want to add 35. then when the table exceeds past its limits you use the "maf table correction data" on the right hand side and gradually increase the numbers on rows where values are exceeding 255. Each small step up brings the values down a fraction, so you adjust this until the whole row is in range (and aim to keep the last column as close to 255 is you can for table resolution). When you do this you dont need to populate cell X39, I think this is spread sheet use as intended.

Then you'd do your dyno pull with the new table and calculate target vs actual AFR as a %, and against maf hz, then set up a new spread sheet updated for your new starting point and only apply corrections to rows where its needed. Repeat until your fueling is good.

Yeah that's what I would have thought too, but Yoda mentioned it should be lower start like with gen 3 maf

The recommendation to reduce was based on the data you provided before you found the MAF wiring fault. Basically you need to get the start point about right and then tweak the table.
Remember an ls7 card MAF is used in a large diameter air intake tube so if you have it fitted in a smaller tube it will have different values. If you know the ls7 tube diameter and the one you have you maybe able to get a ballpark start by using the difference in cross sectional area as a scaling start point.
Also make sure it fitted in a nice straight section of intake pipe work.

Yeah It's still 35% lower MGC & g/s than what the standard maf is so I assumed it would still be the -35% of stock tables, but yeah its in a perfectly round 90mm down pipe section & I think there normally in a 4" or 100mm neck but not positive on that.

The difference between the cross sectional area going from 100mm to 90mm is 19%. This is inside diameter, not sure if the 90mm I'd inside or outside. If inside diameter is 85mm the percentage difference is then 27.75%.
If you have the ls7 MAF curve and reduced by 19% would be a good starting point.
Doing this may be able to leave the start point as it is, main thing is to have first value in the first table similar to stock.

I guess I have to find what car the LS7 maf was released on & the exact diameter of the original neck!

I just thought by knowing the MGC &/or g/s are 35% from what the factory reading is & I want to make all the reference tables for those values as close to similar the easiest way would be to change by that percentage?

These are supposedly the cars that are released with that MAF;
2007 Chevrolet Cobalt 2.4 SS L4

2006 Pontiac Solstice 2.2 L4 - Manual
2008 Pontiac Solstice 2.0 L4 - Manual

2006 Chevrolet Corvette 6.0 V8 - Automatic
2007 Chevrolet Corvette 6.0 V8 - Manual


But not sure what models for Aust, but I did get HP tuners versions of all these but being different engine sizes they will have different size housings!

The maf tables from the corvettes are probably a good starting point. Hz will be affected by differing intake design so you'll still want to dyno it.

The closer the MAF curve is to start with the less tweaking you'll need to do.
There's nothing wrong with doing 35%, but you're using a standard MAF as a starting point and I'm unsure of how similar the ls7 MAF curve is. Being a card type without screen etc it may behave differently. Would be interesting to compare all the curves for the different applications and see how they look.
There are a lot of different things that can affect the airflow so Antus is correct about doing it on the dyno. Intake tube bends, diameter, surface roughness, material, stiffness, etc will all make a difference, some large and some subtle.
It will be interesting to see the final curve and how it compares to the standard curve when you're finished.

I will compare all the curve's of the LS7 maf of the car's I got files from, but not sure how to convert from the way HP Tuners lays them out to the way we have them laid out but will give it a go!