So many questions, first off, it looks slamming sexy!
1 what do you gain by using stainless steel?
2 is it heavier?
3 does the fact that it is made of stainless steel have any side effects on the engine?
4 can more people start doing this?

Thanks for the compliment! I'll answer your questions to the best of my ability, but I don't know the answer to some of them.
1. Stainless is like chrome that won't rust. That is my reason for using it. I shouldn't say it won't rust, but 304 stainless, which is what I used, is very rust and corrosion resistant. Much more so than chromed steel. At kraft we use 316 stainless for everything food contact, because it is even more corrosion resistant than 304, but for pretty much everything else we use 304. It stands up to pretty much everything but the most harsh acids and chemicals and salts, that are used during sanitation.
2. There isn't much weight difference between 304 stainless and mild steel per square foot, at the same thickness. I honestly don't remember which is heavier, but they are so close to the same weight there probably wouldn't be an once worth of difference if the same thickness was used.
3. This is one that I can't answer honestly. The power curve of a two stoke relies on the tuning of the pipe as much as any other factor. The tuning of the pipe relies heavily on the speed of sound. The speed of sound is affected by many things. Heat is one of the things that effects it. I can not say for sure how much the stainless steel will effect this. I hope the percentage of change is small enough that it is insignificant, but it will take a dyno test to prove it. If there is a change, I HOPE it is for the better and it somehow makes more power than the hall pipe!

I THINK it will be fairly insignificant with only a marginal difference than the hall pipe. At the end of the day I EXPECT it to still outperform my old Q v1 pipe.
Honestly though if it is close enough to the Q pipe that I don't see a noticeable loss in power I will be satisfied. The bike runs freaking hard with a Q v1 pipe.

4. Honestly the fabrication wasn't easy. I have 20 years of fab experience and do it professionally. I wouldn't expect most people to be able to pull one off that was nice, however I recall a guy making a hard running pipe out of a microwave..... So anything is possible