Hi all,
I have thought of a way to create a sample played at different pitches and played at the same duration at all pitches with no lag using stock tools.
1.	Take your sample on a track.
2.	Use shift 9 to pitch it down a couple of octaves
3.	Create a custom action combining the keystrokes of control D (duplicate item) and shift 0 (pitch up one semitone)  Bind this duplicate and pitch shift custom action to a key stroke
4.	Select your sample and hit your shortcut key lots until you have about 48 examples of your item and the pitch shift is now plus 24 semitones on the last item.
5.	Double check that the first and last items are playing at the same speed.
6.	Select all items with control alt A.
7.	Run the RS5K action to export item to RS5K drum mode.  In the dialogue for which key to start on, make sure you enter the midi note that matches the pitch of the lowest pitched item you had.  Hit enter.
8.	Once the script has run you can now play 4 octaves of your sample all playing with the same duration and no lag.
Sounds good.  You may want to play around with the pitch shift / time stretch algorithm in item properties  to get the best sounding result for your sample at such large pitch shifts.
A limitation of this system is that by default the RS5K script does not obey note off.  So the sample will play in its entirety even though you play only a short note.  To remedy this you can use the script:
Chessel  Set Last Touched Parameter  To All Same FX In FX Chain.lua
If you update a parameter on one instance of RS5K on the track and then run this script, the value you enter in the dialogue will be applied to all the RS5K on the track.
This means you can set the Obey Note Off parameter easily.  You can then go on to update the attack, release,  and so on.
This script is available in the Reaper Dropbox in the Scripts folder or in reaPack in toni Barth's repository.
Hope you find this useful.
Best, Chessel