Hello Goodlife.
Thanks for replying to this post - which I had forgotten all about!
Since I posted this in 2017, I have tried a few more experimental devices/ chinstraps and found that the best one so far is one that I made from an old pillowcase, folded and sewn into a strip about 2inches wide. This is secured with the velcro-like stuff that I 'borrowed' from an old hernia belt. This cotton material has virtually no elasticity, so once it is secured it stays in place (unlike the stretchable stuff which tends to allow the jaw to drop open when asleep). To make it softer around the chin, I sent for a thin offcut of the sort of material they use for wetsuits, but I cannot remember what they call it. That works well for comfort; As an aside, I also have a small piece of velcro material that secures the airpipe to the centre of my chin and then on to the CPAP machine via a longish tube.
If these sorts of devices don't work for you, I would suggest you try sleeping in the 'hammock-position' which tends to use gravity to keep reflux at bay and therefore reduces the swallowing of air. ( I have a purpose-built bed for this but I think the same effect could be obtained with cushions and/or or pillows.
As for the potential output of faeces or gas; I would strongly recommend wearing an irrigation sleeve at nights, (folded to make a large bag) rather than a smaller bag which, like you indicate is likely to be a bit vulnerable when full.
I can almost guarantee that you will not be filling an irrigation sleeve and they are so much easier to empty and rinse out than ordinary bags.
I have devised my own baseplate for the irrigation sleeve so that the bottom part of the two-piece device is semi-permanent and the bags I can keep re-using daily and nightly for about a month, until they become too soiled to bother about. The boxes come with about 12 sleeves, so they last me about a year; the clip-on base has thus far lasted for about 3-4 years. (This can be viewed on my profile photos) I stop it sliding on the skin/mucus by spraying around the hole with medical adhesive. Also, My design for the baseplate includes a 90degree waste bend, which channels any output down into the bag, rather than allowing it to potentially pancake around the stoma. It's not everyone's idea of a solution, but it works for me!
Yet another slight adaptation is that I have inserted a medical filter in the CPAP output airpipe to filter out any impurities in the air. (we have a problem with air purity in our area with vehicle fumes and industrial pollution!) The CPAP pressure needed to be turned up a bit to compensate for this and the albas oil is now dripped directly into the air tube nearer to the mask, rather than in the water condenser. It was interesting that the filter worked so well that it filtered out all the smell from the oil and nullified its effects. Hence the change to nearer the mask and away from the filter.
I hope this gives you some useful ideas you can try to resolve the issues you are presently having.
I will finish by stating that many of my experiments have worked, but there is always room for improvement, so if you find something better, then please let us know.
Best wishes
Bill