I need different lengths and sizes in thickness. GTX 1080 Ti needs a lot of them and in my country they are expensive and not always available in all sizes that's a problem without a doubt.
I rather buy arctic thermal pads in all needed sizes for 32 eur. Not for 80 eur or more that's just ridiculous it's actually 1/6 price of actual video card.
Spending 80 or more eur for thermal pads definitely is not worth it!
I have already pointed out you cut the pads to fit.
FITTING THE PADS
This is how I fitted the pads, you have to cut them. Also try not to touch the pads with your fingers when you remove the protection on both sides of the pads, you don't want to contaminate it.
I did not manually compress the pads, I allowed the base plate to do this when you screw base plate & PCB together, but you must never take it apart again, it has something to do with the way the pads compress & hardened overtime. So to check you have the right thickness you may want to apply a small sample on just one VRM or one memory chip just to check you have the right compression. You can still use the sample pad again as it is still fresh. Of course, do not power up the card with just one thermal pad on VRM or memory.
When you have fitted pads to all VRM/Memory you must not take the card apart again, as you may not have the same compression, this is all down to the type of thermal pad. Not all thermal pads are like this, it's all down to what type of thermal pad user(s) have installed.
17W/mk pads is what I use on my R9 Nano VRM (1.5 thickness), I don't think such high level pads is needed on memory chips.
Also I did play around with stacking the pads, as I have a lot of it & I did not detect drop-off in performance, but I used a lot of thermal pad as it does break-up under excessive pressure. This was just a experiment in stacking thermal pads.
About stacking thermal pads will it be fine to stack them 1.5mm + 0.5mm or 1.5mm + 1.5mm ?
When thermal pad is placed on the video card does it holds in place when pcb is upside down without cooler ?
You can stack them if you have the wrong thickness, but you have to be careful of cracks/break-up of this type of thermal pads. I would not go higher than 1.5, but if you want to experiment, do it on something you don't care about & not on your main computer.
This type of pads do stick to the R9 Nano "metal" MOSFET with a gentle push, but I also cleaned both surface with Isopropyl.
Compression must be done when PCB & MOSFET cooler come together, this is key. Too much movement under pressure will do too much unnecessary spreading of the pads, in other words, use the screws hole & screws to align PCB & MOSFET cooler, & when you screw the two together, compression will be done. You don't have to follow this route, it depends on "what type of pads you are fitting" & you can mount it as normal if you have the other type of pads, but i'm getting absolute maximum heat transfer as i'm allowing the cooler & PCB to do the compression for me. Also it looks like 1.0 thickness is the correct one for my card, but I got away with 1.5 without it breaking-up.
Do a sample test, then take it apart to give you an idea what's happening when you put the two together, but you don't have to do this, if you are using another type of thermal pad.
EDIT UPDATE @OP
Download Docs for your type of thermal Pads. It looks like your arctic type of thermal pads is straight forward, so you fit them as normal & skip what I have said in this thread.