Rear belly skin

Hi All, the rear belly skin started of flat however after riveting stringers to it and a couple of bulkheads which curved it at the sides as expected I notice the skin doesn't sit flat on the table longitudinally anymore. I heavily clecoed the remaining parts and clecoed the side skins on. It all seems to fit with no warping or billowing of side skins but took a bit of pushing in the middle of the bottom skin to get the holes to line up with side skins.
Is this expected or have I induced a longitudinal curve in the bottom skin?

Rear Belly Skin

If someone could run a string line longitudinally from the front of their rear belly skin to the tail wheel cutout along the centre line to see if this skin remained flat after rivetting I would really appreciate this. I am looking to pull a stack of rivets out and have another go if rivetting results of others show that it should be flat.
Thanks in advance.
Scott do you have any advice on this please?

I just looked at mine and while I can't say mine is straight edge flat, there is no significant bow in the bottom skin. When I attached the lower side skins all of the rivets fell right into the dimpled holes and no massaging or muscling necessary. I couldn't find a straight edge long enough to run the whole length but I would guess any bow was under 1/8" from end to end I think that is just because the front part has no bulkhead to keep it down and will be ok once it's mated to the front fuselage section. Do you have a pic or measurement? I just know any time I needed to muscle any part into position it has been because of an error earlier somewhere.

Belly skin

Thanks Chris appreciate you having a look for me.
I have worked out that I used to much enthusiasm and not enough grey matter.
I back riveted the stringers and to keep the assembly off the clecos I used a two inch block of wood to hold the back plate high enough. This should not have been an issue except I held the back plate and wood block together with three layers of masking tape each end making the ends slightly more elevated and as I back riveted I induced the bow in the stringers.
Inverting the assembly I was able to press it back flat using my hand shaker. No one was looking so I think I have got away with it! Build on they say and thanks for your help.