I have modded my mates gt5.0 with no problems. Same situation as you, I think the gt5.1 is when you get to certain amount of cars and stuf.

I Believe GT5.1 Is For The Portable Garage. GT5.0 Is The One To Mod.

GT5 uses GT5.0 to start with, when that file hit's the limit, it continues with GT5.1 and if needed with GT5.2
By then you have 2000 cars, 3000 paints, all museumcards/all horns and a bunch of gear

Be aware, it becomes really slow to load...

All important information for hybrids/credits and stuff like that is located in GT5.0.
There are exceptions in other things which you need to find in GT5.1/GT5.2.

So but for standard stuff, decrypt GT5.0

Can you get chassis/engine etc swaps to work with a bigger save file though?

I tried it earlier on my main save (has GT5.0, GT5.1, GT5.2), which resulted in losing all cars in the garage

Sure, use my tool, in the other thread.
Which works with your current car in use.
The current used car is located in GT5.0

So I should be able to do that manually too... will have to try it again later . Thanks :y:

Now I just want to know how to delete those effing museum cards lol

Or disable receiving new ones lol......

One checkbox too little PD coded

One way to solve it, is to change item number to 7000