Here is a technique you can use to resize a response window or userobject as needed. It makes use of the GetWindowLong and SetWindowLong Windows API methods. The oldest reference I found to this is from Eric Aling back in 2000.

In a nutshell, you are changing the border around the object to one which Windows allows to be resized. What's even nicer about this is the standard resize events are triggered so you can reposition/change objects within the window as well (PFC resize service for example). From Eric's original post:

"The Get function retrieves the complete definition of the window in 
a big long variable. All the bits in this long value describe the window. 
So there are bits for the type of border (which indicates if a window is 
resizable), menu, colors etc.etc. We can modify this long value, altering 
the design of the window. Using the SetWindowLong() we update the window with 
our specific modifications."

I used this in ancestor code of a userobject I use to create visible panels within the main window.

// Unicode declarations, used 'A' for ANSI
function long GetWindowLongW (long hWindow, integer nIndex) Library "user32.dll"
function long SetWindowLongW (long hWindow, integer nIndex, long dwNewLong) library "user32.dll"

// code in my post constructor event
n_cst_numerical lnv_num // PFC numeric service
long        ll_Styles
boolean        lb_Control

constant long    WS_THICKFRAME = 262144
constant long    WS_SYSMENU = 524288

ll_styles = GetWindowLongw(handle(THIS), -16)
if ll_styles <> 0 then

    ll_styles = lnv_num.of_BitWiseOr(ll_styles, WS_THICKFRAME)
// don't need control menu but leave this for reference 
//    if ab_Control then 
//        ll_styles = lnv_num.of_BitWiseOr(ll_styles, WS_SYSMENU)
//    end if

    SetWindowLongW(handle(THIS), -16, ll_styles)
end if
At first my UO cannot be resized.

Now it can!

I've seen other references to these API calls for manipulating windows for other things but I have not investigated further.