As it happens I did both front and back windows
on my 75 boler twice in the past couple of weeks. The first time I put the original seal and lockstrip in only to find that there was a tear in one of the seals that would result in a certain leak. I ordered new material from Scamp
and then did them again. Putting the windows into the original seal was slightly easier than the same operation with the new rubber because the old stuff retained the shape of the corners while the new was straight and didn't want to make those tight turns.
It is not a really difficult job and I did it without anyone around to help. A second set of hands would certainly make it easier though.
Here are a few things I learned.
1. You really need a lockstrip tool. I used that and an old butter knife to get that last tough corner in.
2. Some form of lubrication really helps. I used Dow Corning 111 Valve Lubricant and Sealant that I found at Acklands. I tried to get in to the channel the plexi fits into as well as the lockstrip groove. Lubricants suggested by others may work better as this stuff is pretty gooey.
3. If you are putting new rubber in make sure you leave a good half an inch of overlap after fitting it into the opening before cutting. I ended up with a nice tight fit at the ends with the new rubber.
4. I read on an automotive site that the lockstrip should be on the outside of the vehicle because the system is designed to tighten when air pressure is applied to the lockstrip side. Pressure applied to the other side may result in the window coming out of the seal.
5. Due to the requirement in 4, be very careful of your new paint
job while using the lockstrip tool. A lot of pressure is required to spread the seal and the thing likes to pop out and hit new paint
If I have missed something or if you have any specific questions let me know and I will try to answer them.