I use Boingos all the time with my contour or prefolds. I have found though when using them for overnight to back them up with pins.
I've had a couple times had one come loose during the night. In the mornings when I get up the front of my diaper is fully soaked.
It could be I might not have stretched it tight enough. I also move quite a bit during the night being a side sleeper and turning from
side to side. I've never tried the Snappi's. I've been using the same set of Boingos now since April. I wear cloth in the late afternoon
till the next morning every day.
Also I wear size large in my contours and prefolds. I don't think the Snappi would stretch
that far on my size large prefolds.
I used the larger size snappies.
It was a bit tight but it worked amazingly well.
Now that I've grown a bit in my legs (I workout a lot), it's too tight for confort unless I change my prefold to larger size.
IMO, Snappis only work well if you're on the small side, or else if you use more than one of them (e.g., one per side). I have a 38" waist and found that, to use a Snappi, I needed to wear an XL prefold (Changing Times) and fold it down. Otherwise, the back corners of the diaper simply didn't come far enough forward for a Snappi to reach them. Snappis are small and don't stretch much. And the bulk of the XL prefold was not enjoyable. I normally wear a medium. Also, becuase a single Snappi only supports the very center of the front of your diaper, you end up with a very loose feeling through the folds of your crotch -- not very confidence-inspiring. I like a very snug fit, and I find that a single Snappi just can't provide that. Dual Snappis are much better, but then you've lost most of the convenience factor. Pins are easier than dual Snappis, IMO.
I have Boingos also, and I use them fairly often. Because they are used almost like diaper pins -- one per side -- they are better-suited to a variety of diaper sizes and body shapes. I find that they do a good job of keeping my medium prefolds nice a snug. I have observed that they get a little stretched-out over time, though. They are much stretchier than Snappis, and if you are on the large side, or like to add a lot of extra bulk/weight to your diaper, you might find a pair of Boingos inadequate. Some people use four Boingos -- two per side -- but as with dual Snappis, this erases their advantage, IMO.
Ideally, somebody would make Boingos tuned for adults.
I use the snappy and a bath sheet towel for my cloth nappy as well as plastic pants and a onesie to help keep it all in one place.
I find that the use of two snappy holds the nappy in place very well I've never woken up with a loose nappy it fells firm all the time. I found also when applying the nappy to make sure that you fold the nappy down at the back and in at the buttocks before bringing it over your crouch it give a much firmer fit. check YouTube out for more details