I do have a 2000 Deg F oven... Hmmmm!
Yes, I used a bic pen and cut the pen to the right length and used that for a guide. I cut the roll pin a little shorter to ensure it will fit in far enough.
A few things to know when using the roll pin for the negative post.
1) Make this your first step, as the body of the SGV3 will get hot!
2) Once you put it in, it is in, good luck trying to get it out. Make sure that it is ground down enough and you don't seat it too far into the hole. I cut mine using a Dremel cut-off wheel, I used a bench grinder to grind the first one, using the Dremel tool is much easier.
3) Make sure you heat the roll pin up enough to get the solder to hold to the inside of the roll pin and not to just to the top were it was ground down. I had one nail come lose because I didn't heat it enough with the soldering iron. The first one I did with a butane tourch. However, I've been using a soldering iron for the others, just make sure you are patient and heat it up enough.