Recommend pulling out the Captains seat post to make sure it is a really long one. You would want it to go down into the seat tube to the depth of the lateral tube. Otherwise, you might break riding with the seat up that high. I found really long seat post on Amazon in the $10 price range so it wouldn't be a hugh hit to fix.
Re the frame; The very short headtube puts some real limits on the overall strength. On such a small frame, designing it to use a smaller diameter wheel would have been a good idea or using a stepped top tube to get the rear toptube down low like it is without requiring the front top tube to be so low which led to the small headtube, etc. The down spec'ing for Nashbar sales (at a lower price point) from the original full chomo tube Yokota spec's probably achieved by downgrading the top tubes, rear stays and the lateral tube from chromo to hi-tensile steel, thus leading to the quasi-marathon design and the crossed/overlapped lateral tube. Hopefully the folk is chromo....