Cvt RPG III to RPG IV (strange problems ) -- RPG400-L

I have finally bitten the bullet and converted all our RPGs to RPGIV.
Occasionally I see questions asked about the reason to convert and
see the standard reply's about better functions, modular code
more modern techniques etc. I wonder what others have experienced.
This is a brief list of GOTCHAs i got.
I am NOT using ILE.  I have NOT converted the CL to CLLE.
We still have a mixed OPM environment as we have a lot of AS/SET
generated programs.  We have upgraded AS/SET to V8 and it
generates RPG IV code but have not as yet recompiled all the
AS/SET programs.  We are at V4R5 and  SF66442  is highest PTF.
Everything is compiled to run in  DFTACTGRP but I am getting
strange things happening.
RCLRSC is doing funny things, particularly if I do RCLRSC(*CALLER).
When I read the manual I get the impression that RCLRSC is basically
obsolete and for RPGIV pgms only works in DFTACTGRP and if invoked
from the top program in the call stack, but what is the top program.
I have a menu system that is OPM based and is usually the top
non-system program in the call stack.
I have to be really careful with SQL programs CRTSQLRPGI.
CLOSQLCSR( *ENDACTGRP)  is the default whereas with
CRTSQLRPG  CLOSQLCSR( *ENDPGM ). Cursors are staying open
when I expect them to be closed. Perhaps I should change the
(*ENDACTGRP) to (*ENDMOD) permanently.
When the SQL cursors remain open and the file was locked
with ALCOBJ occasionally the lock REMAINS even when the user
 has exited the program completely.
OVRDBF's can stop functioning, all it takes is for a program to be
compiled into some other ACTGRP, but usually this is quickly
visible in the call stack.
I have dabbled with ACTGRPs and modules and service programs
and have concluded that ILE is a bit of a Pandora's Box.  If one is not
very careful with the system design and system standards one is
going to have problems.  These problems are going to be manifest
as application errors, but are really system issues and it will not be
easily fixed by correcting a bit of coding.  I am in a Catch-22 here.
What is the system stardard I need to adopt, I wont know until I try
something then changing the system standards can mean a lot
of backtracking.

Let me say that I have written from scratch a small application using
ILE and SQL. There are some things you simply cannot do in OPM.
I now have a powerful modern tool at my disposal.
The power of SQL is more easily used in an ILE program, NULLs, DBCS etc.
But power is a two edged sword and everthing has a price and in
the case of ILE the programmer needs to be more skilled than with
OPM, either that or more constrained by system and shop standards.

Frank Kolmann