Hello
I have bounced exactly into the same problem, and before posting a new thread, I found this one.
Since then many years have passed, I am using Inventor 2012, but I still can not do what you originally asked/requested.
I created a part (attached), which is practically a simple cylinder but constructed in a bit complicated way (length of the cylinder is driven by the first, unconstrained sketch - I did it like this because for the final, more complicated part that I wanted to create, this way was more adequate). When I made the first sketch adaptive, and placed this cylinder adaptively into an assembly, I could constrain its two endplanes to other geometry, and it adapted its length.
As soon as I made the cylinder an iPart (its diameter being a custom column), it lost adaptivity, I could not anyomore adjust its length within the assembly, adaptively.
Is there a solution for this?
Inventor Pro 2012
Hi! I would like to offer an opinion technically. Adaptive and iPart are actually mutually exclusive at the moment. The reason is pretty straight forward. iPart/iAssembly was designed to be table-driven components. The definitions of the iPart/iAssembly should always be driven by configurable items on the author table. Any attempt to alter the iPart/iAssembly outside of the table can run into roadblocks.
Adaptive is at technology allowing you to define or drive a particular part (and its occurrences) within an assembly it is in. Adaptive is context-sensitive, while iPart/iAssembly is not context-sensitive. This means an adaptive part can vary due to factors within the assembly. iPart/iAssembly will never change independent of where it exists. All definitions should be elaborated on the table.
Many thanks!