Classic & Vintage - Length of LaPrade fluted seatpost?

I'm in the process of extracting what seems to be a galvanically welded SR LaPrade seatpost from an early 80's Univega Sportour frame. It's been slow going and very frustrating. After about four hours of hack-sawing, I now have the post cut into five slices vertically, but all I've managed to do from there is to break off the top inch or so of two of the five slices. Right now, I have the bottom of the seat tube corked, and the tube is filled with ammonia and soaking for a while. If this doesn't work, I guess lye will come next.

This is the post that used four vertical clamping plates with a square bolt running transversely through a short cylinder at the top of the post. There is one of this style on ebay (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300096108019) right now. Mine looks about as short as the one listed, but I'm having difficulty getting a good view down the seattube. I've hooked what feels like the bottom of the post with a bent hacksaw blade, and it seems to be only about four inches into the seattube. Anyone know for sure? Did these come in longer lengths so that perhaps I just haven't cut deep enough down the seattube?

Also, when and if I get this sucker out, does anyone happen to know the diameter I need for the replacement? I've been assuming that a Univega of this vintage used 26.8, but this model is not in Sheldon Brown's database.

My first bike was a Univega, and it took a 26.8 seatpost. I bought a nice long alloy one to replace the short stock seatpost, but I kept it when I sold the frame. I've flipped a few Univegas since then, and that seatpost has failed to fit in any of them...even the same model a year or two apart. Measure the iner diameter of the seat tube with calipers, or just bring it to your LBS. It should also say the size on yours, if you can still read it in the end.

I've got at least three of those posts, and they all look like the one on ebay you linked to as far as the length is concerned. There may have been longer LaPrade posts than that, but if so I haven't seen one. Good luck getting the stuck post out-

I'll brb with the measurements...

well, now that I look at the one in the picture, mine isn't exactly like it, but FYI, mine, along the front of the post from the end to the base of the clamp area is 19cm.

Take a length of coathanger with a small hook on the end, run it through the seatpost and hook it on the lower end. Mark the hanger with a felt tip, withdrawl and measure. Viola!

Take a length of coathanger with a small hook on the end, run it through the seatpost and hook it on the lower end. Mark the hanger with a felt tip, withdrawl and measure. Viola!That's pretty much how I was doing it with the hook-bent tip of a hacksaw blade (I've gone through four of them so far; they tend to hang and buckle.). But for some reason, there does not seem to be a distinct spot where it hooks. It almost feels like the bottom end of the post has been finished to an edge. The walls of this post are a good 5/16" thick at the top, but the center opening gets larger as it goes down.

Virtually every SR Laprade I have come across has been 26.8...if that helps at all...