This build is from a casting and is fully functional other than the main spring.  I did put 3 round threw it today by just clamping a spring to the lower tang, crude but it worked.

My problem is where the main spring mounts on original guns.  I've been told it needs to be attached to the top tang and this could be confirmed correct by looking at the De Haas diagram because that is what it shows.  But, digging around on the internet, and from my  photos of original guns, it appears that it might be attached to the lower tang.  I have added 4 photos to this post to generally show what I am seeing.  If the spring is attached to the top tang it is attached with a blind threaded hole because I'm not seeing a screw coming through the tang in any pictures I have found.  On the other hand, I found several guns that have what appears to be a screw coming through the lower tang just in front of the wood screw.  So...I would never ask anyone to remove a stock from an expensive gun but would like to know if anyone might have a photo of a #7 with the stock off, or if not, can possibly confirm the location of the spring, top or bottom?  I'm fully aware of the coil spring conversion but I'm preferring to go with what was originally done. 
The first picture is the top tang of a gun I took photos of.  The second is a lower tang view taken from the internet.  The others are side views kind of hinting at what they have.
Thanks,
Bob

That was fast, thanks.  I wonder where De Haas got his info!  I don’t suppose I would be lucky enough that you got pictures?

Bill, I did take a look that way and the schematics I found do show it on the back.  But there is a big difference in the shape of the tang between the two so not sure it helps.  Thanks though.

I didn't take pictures as I wasn't at his house to take pictures when he had it apart. I do recall the mainspring had a dogleg, or hump to it to correct the angle from front lower or front tang to the hammer angle.
Which of DeHaas' books shows the #7? I looked at my copy of his first book, "Single Shot Rifles and Actions" and it's not even listed? I have all his books, but haven't looked in the others yet? Is it in his Gunsmithing Single Shots book? Not sure why he'd show it attached to the top or back tang?

I had a good friend who years ago purchased a "#7 Rolling Block" in .22LR and called me excited to tell me about it. We arranged to get together a couple days later so I could see it. He got it at what was a very good price for these rare rifles, and the condition was minty, as a restoration.
When I first handled it I immediately felt like something wasn't quite right, but not having examined a lot of them previously I didn't say anything. But the more we looked at it, the more I questioned it's authenticity in my mind. I finally asked him if we could pull the stocks off and check to see how it looked internally. On removing the forearm I could immediately tell it was a replacement, as was the barrel. But being restored we didn't expect different. But when we pulled the buttstock we immediately saw the welds that had been done to reshape the tangs, and knew it was a well done (externally) fake. 
The gun likely started out as either a Rolling Block pistol, or a #2 rifle. The top tang had been cut off, and a new tang shaped and welded on. Then metal added to get the hump where the sight would sit. That's the area that made me question it before taking it apart. That and the tang sight itself looked a little off.
The lower tang was bent, and the mainspring was custom built and attached like originals I'd seen. Overall, at a glance, or to someone totally unfamiliar with the #7 it looked good. Just not great.
My friend passed away a few years ago, and another friend sold his guns for him. I asked about the fake #7, as I was interested in buying it, if it could be had cheap enough. But he said it wasn't found, so likely my friend had already resold it, and someone else has it now.

Here's a post on the Remington Society's page that is a good source of some details on the #7, but doesn't cover the mainspring.

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Your description of it being like the Stevens mainspring is spot on! That's almost exactly how they looked to me. 
Not sure if DeHaas was imagining how the old pistols were reworked into a #7 by Remington workers, or why he'd show the spring attached to the top tang as shown?

art..22 lr

Thanks Bruce!  Didn’t know what it looked like but had an idea what I thought. Made one today that looked nearly identical to yours.  The only problem I didn’t make it heavy enough.  If I would have stuck with my original plan it may have worked, but didn’t and thinned it down at the last minute because I thought it was to heavy.  Oh well, I’ll make another in the next couple days.  Again thanks, that picture is a big help!
Bob