The Gaavad of Jerusalem was asked by someone if he may make a Minyan of Tefillin wearers on Chol HaMoed.
The Gaavad suggested not doing so but rather putting them on privately.
Thereupon the questioner asked if it was Osur to do so.
The Gaavad answered that he would not say that it is Osur, just that he recommends otherwise.
But as I pointed out before, that three big poskim of Bnei Brak have ruled that one may put on Tefillin on Chol Hamoed with a mniyan and so Rav Scheinberg rules as well.