Well, looking at it from a conforming lenders standpoint, you are asking (one scenario) for $210k to complete one more duplex, while the lender would be paying off a first of $160k. So before closing costs etc. you have a $370k loan against an appraised value of $450k. Take $360k/$450k and you have an LTV of 85% (over 80%). With a 610 score, that's not going to happen except maybe in a JV loan.
Or look at it another way, according to the appraisal, you have two duplexes (I am assuming that based on the posts but I could be misinterpreting that), meaning even with the additional land they are worth $225k each. Lending $210k for finished value of $225k would again mean lending at 95% LTV. That's just not realistic for normal bank lending.
Also, based on the figures I am using, I only see the property being worth a tad over a million rather than two, if you drop 3 more onto the land.
But this is the hard part of only getting the condensed information. If I had the appraisal in front of me along with your proposal to the banks and breakdown of income and expense for the properties I could probably narrow down your issue.
Unless I am missing something, I would venture your only option is JV money currently.