You would do better to treat the magnesium scraping as a booster for your tinder ball. Rather than as a initial source of fuel. I know what the packaging on the DOAN and Cohglan magnesium blocks tell you to scrape it into a hollow etc but in practice it does not work. At least not well.

In terms of using char cloth: What is wrong having it burst into flames if ignited with a ferro rod? That is after all what you are trying to achieve when you strike a spark into it with a carbon steel striker and a flint and insert it into your tinder ball. All you are doing is saving yourself a lot of huffing and puffing. Note* Char cloth is worth having in you kit because it takes a spark from quite "cool" sparks. Like those struck from a carbon steel blade with a flint. The trick in it's manufacure is to avoid heating it too much to quickly. There are a couple of good short video's on YouTube. Use the search words BUSHCRAFT & CHAR CLOTH.

When stainless steels first came on to the market ( as 440A & 440C etc) they were relatively crude in terms of their metallurgy. Brittle, edge retention was very poor etc. Where as carbon steel has been around since the dawn of time. So it's a well understood metal. However, stainless steels have taken a quantum leap since then. Metals like 154CM & VG10 will give sparks from a ferro rod that compare very well with high carbon. To illustrate that point: The Swedish Air Force selected VG10 for the F1 survival knife. That's a stainless steel. The one thing that I have found to be critical is the shoulder of the spine on the blade. If it's rounded off as many knife producers do for a comfortable fit and for aesthetic reasons you are going to have difficulties in getting a decent spark. That is because the spine is riding over the rod rather than cutting in. Knives like the F1 are manufactured with a sharp spine for that exact reason. it's a mistake to assume that all carbon blades will automatically perform better than a stainless one. The ratio's of carbon to iron and the amount of oxygen applied to the smelting process, the forging of the blade and how it's quenched will also make a dramatic difference.