I am a hold-out in my work-world for using non-fusibles to support the hems of garments. In fact I prefer to not use them at all except where really necessary, but I digress.
What is in your hem? There are many options and if you look inside a modern RTW suit jacket there may be a small area of fusible in the hem allowance but what holds your hem up?
It is very likely that the lining, and a small tack of stitch witchery is all that holds it up. Your sleeve and body hems are likely not stitched anywhere.
We tend to stick (no pun intended) with more traditional support in the hems like this piece of bias silesia. This silesia is cut on the bias so it can be slightly shaped as needed and has some give to it. It is laid in place so that it extends past the fold of the hem. It is stitched in place in the fold of the hem and along the vent with a small hand made pick stitch, barely noticeable on the right side of the fabric. The silesia is cut wide enough that it extends the height of the vent- and it gives you something to stitch to when hemming the garment. In the photo above, you can see that Denise has put in a large and loose cross-stitch along the upper edge of the silesia to keep it in place, and has basted the vents and the hem up in preparation for a first fitting.
You can use other support fabrics like bias linen or canvas- whatever is suitable for your purposes.
The problem with fusibles is that they become de-laminated in many cases especially with the amount of wear and tear and cleaning that our suits get. When fusible delaminates, you will see a bubbling on the right side of the garment and it can be almost impossible to re-press and re-glue it.
I figure that if we are making things to be used again and again, the time it takes to do this step is well worth it when you are faced with taking a whole hem down in a delaminated situation. I've also seen a few examples where whole jacket fronts have delaminated and while it may have been a time saver when the jacket was being made, I think it is false economy if it cannot be used again.