A lot of times these were made for aircraft that no conventionaol kit was made and in many cases the vacuum kits are still your only option. Some companies did high quality vacuum kits, Rareplanes being one. Others, like the two I have were not as good.
I have two vac kits myself, a C-140 and a T-39, two utility aircraft from the 1970s. I have the T-39 started but thinkg keep getting in the way of finishing it. Eventually I will.
With the vauccm kits you have to cut around the parts, leaving some excess exposed. To get the parts ready to glue you will have to take a sheet of sandpaper, possibly stapled to a piece of wood or just flat on a counter or desk top and sand each piece until the excess is free.
Parts most likely would have to be re-enforced with scrap plastic to give it a larger area for glueing.Plastic strips or a couple sheets would work.
You may also have to eithre build the landing gear from scratch or in some cases find brass wire to put into the gear halves if provided. You could always just mount your project to a base like it was inflight to save time and work. That is most likely what I will do in the end.
What is the aircraft kit you have and who made it?