Hi Paul -
If you just want one of us to try the file, you can upload it here (as an .svg) and one of us can try it. What program have you used to design it? My concern, tho, is testing the design with the actual media you are using. You said it is 100-150 gsm. That designation always throws me because that means different weights depending on if it is coated or uncoated card stock etc. For instance, 150 gsm is about 100 lb card stock - which is a heavier cardstock than 100 gsm which is more of a light weight paper and will usually cut a detailed folder easier than a heavyweight. Again, a lot depends on the file as well.
10 minutes a sheet would be a VERY long time for a file - I cannot imagine a file taking that long to cut - to engrave yes but not just to cut. Remember that if a file is node intensive, it will take longer to cut because the machine will read each node as a "command". And depending on the detail, even tho the Silver Bullet tends to cut detailed files better at a faster speed, there are times when you need to slow it down a little to get detailed areas to cut well. There are all sorts of factors involved including if you have a lot of curved areas vs. angled areas etc. What is the finished size of an average project? You say A4 which is approximately letter size, but is the file that size? Obviously that plays a factor too - but all of that aside, I rarely have a file take longer than a minute to cut - most well below that. But all of the factors above have to be taken into consideration and may initially take trial and error to get the best force and speed and blade (you may get better results with the detailed blade). Once you get it figured out then the process will be just a matter of putting it on the mat and letting the machine do what it does best!
Sorry for the long answer - I just want to be sure you consider all of the things involved that could make a cut more challenging. That's why I think testing the file and media you wish to use (or give us the weight so we can at least try to get close to what you want to use.
Hope I have not confused you more.... feel free to upload the file or send it to be at
Gigi@silverbulletcutters.com and I will be happy to look at it and try it on some card stock that I have here.