Hi Shaun
Think we must work in the same industry as my predecessor did a similar thing.
Like you I did not feel comfortable with using casks as they are pain to line up properly.
I have used the barriers you mention, they are okay as long as the wind isn't blowing a hoolie if you have the feet in line with the barrier.
I have managed to get round the issue of using the chicane by joining the new kids on the block (iTRUK) as they have effectively done away with the chicane and operating the truck to the test written in the 1960's.
Are you using Industrial Racking at any point in the training or is it purely outdoor training?
Do you have any empty IBC's or stillages you can use if you need to create a barrier?
Are you training novices or experienced operatives?