Hi and first of all welcome to the forums.I don't see why not.Check on the Outwell site at the the width of the minnie 4 and compare it to your monty 4.
I too, am fairly new to this site and to the wonderful world of camping and the advice I've picked up from the wonderful people on this site has been invaluable! I've also got a Montana 4 and asked a very similar question to yourself on 17th August. A very helpful site member sent me a picture of their Montana 4 with a Minnesota extension and it looks great! It has been a difficult job finding one for sale however but I eventually managed to find one yesterday! Mind you I had to drive a very long way to get it in time for our weekend trip away next weekend! My friends and family think I'm mad but I've really got this camping bug! Not yet tried it with the tent but hoping to do that tonight! Will let you know how it goes!
Thanks for your tips, was able to follow links and found your original posting and the photos of the extension.
Looks like it will fit - though I would love to know how you found it if you get the chance-so now I just need to go and find one, luckily 3 weeks until we go away again
Thanks
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Managed to put the extension up last night but didn't get time to set it up with the tent. It certainly looked as though it's going to be ok tho, it's the right width anyway. I was quite pleased with the extra room it will hopefully provide! Going away with it this weekend so will test it properly! I hope it proves its worth though because I went on a round trip of 250 miles to get it. It certainly needs to impress the OH who thinks I'm crazy! Best of Luck