Ambush is a terrible line for indicator fishing since the head is only 20' ish, and then the rest is shooting line. You can put a tip on there, but unless you are fishing super close all the time you might have mending issues. It will turn junk over though, for sure. But the match on that rod would be an 8wt ambush (adjust to taste). Super line for a lot of other stuff. The indicator II is a fantastic line! That is what I use on my 10' 8wt and I personally find it handles heavy indicator rigs with ease - but with that one it is usually from a boat, so maybe cheating. If it is just that your junk is too big maybe you could try a longer rod. Personally I never feel any real joy of any kind casting an indicator rig - I'm going take the Calvinist position here and just say we were just meant to suffer in that case. And adjust our technique to make life merely bearable. :-(
There are, on the other hand, such things as mending shooting lines, if you use a head and not an integrated line. They have a fat mending section followed by a shooting diameter section. Maybe get one of those to attach to an ambush head. Steve Godshall makes one ("mendmaster running line" I think he calls it), and if I am not mistaken there are some other commercial ones. As with all lines with a fat mending section your casting distance will suffer a bit, but like I said, God meant us to suffer when indicator fishing!
Now if you want to go all "Unitarian", and experience pure joy, try swinging nymphs instead!