Flattening Posters?

I have posters still in tubes I plan on putting in a portfolio, I don't have room to lay out a poster for more than a day nor is the floor space safe due to room and dog, any ideas how to flatten posters with limited space?
0
Comments
http://www.jerrysartarama.com/discount-art-supplies/portfolios-and-presentation/picturesque-pro-presentation-cases.htm
~not a dude~
2010: MSGx2
2012: Made In America
2013: Pittsburgh, Brooklynx2, Hartford, Baltimore
2014: Leeds, Milton Keynes, Detroit
2015: Global Citizen Festival
2016: Phillyx2, MSGx2, Fenwayx2
2018: Barcelona, Wrigleyx2
Or you could leave it right side up and put a weight on the top so the folds stay closed/posters stay flat.
~not a dude~
2010: MSGx2
2012: Made In America
2013: Pittsburgh, Brooklynx2, Hartford, Baltimore
2014: Leeds, Milton Keynes, Detroit
2015: Global Citizen Festival
2016: Phillyx2, MSGx2, Fenwayx2
2018: Barcelona, Wrigleyx2
~not a dude~
2010: MSGx2
2012: Made In America
2013: Pittsburgh, Brooklynx2, Hartford, Baltimore
2014: Leeds, Milton Keynes, Detroit
2015: Global Citizen Festival
2016: Phillyx2, MSGx2, Fenwayx2
2018: Barcelona, Wrigleyx2
BTW, what Out of My Mind and Time said about letting them just sit after taking them out of the tube and loosen up themselves for a while - that's good advice. I do that too. I tried to rush it once and forced it flat right away with weight, and it ended up with a kind of ruffle-ish edge or whatever you want to call it. The paper just wasn't ready to be flat yet.
LIVEFOOTSTEPS.ORG/USER/?USR=435
LIVEFOOTSTEPS.ORG/USER/?USR=435