Started my first job using fostapex for secondary loops in hot water heating application. I am crimping the fittings first and then tucking the fostapex between a joist and wall header for part of the trunk run. When I try and flex the fostapex to get it into place after fittings are crimped, I notice the fittings with tension appear to slightly pull away. But once in place I can verify that the fostapex tubing is visible in all thee windows on each fitting. I wonder if this is normal for the fostapex product? If I was using straight up PEX then the pex could be flexed independtly of the fitting. But the fostapex is so rigid I cannot seem to prevent slight degrees of tension being applied to fittings while working fostapex trunk lines into place. I just hope this behavior is somewhat normal and I won't have leaks or gushers to look forward to.

if you are using the viega press sleeves you don't have to worry about a strain on the crimp. it is a double crimp so it would take an extraordinary amount of stress to make it leak. anyway, when the hot water runs thru it any stress will be relieved..
you always crimp it a second time after you have it in place.

You kinda lose the advantage of pex, by making a crimp and hiding it, no?