Not for the purpose of testing the RIC aid. You’re better of by either using a powerdome/dome with a minor vent or by creating a soft custom mold from artistic two-component silicone paste. (See this thread.)
I found that with RIC, you get the best results with combining a vented dome and paste. Haven’t posted it though, because…lazy…Anyways, use few grams of paste behind the mold around the receiver and stick a bendable stick throught the vent and the paste. (When you remove the stick after hardening you’ll have a vent: Drilling is not very nice since the receiver is too thick and the paste will rupture along the vent canal. I use the green sticks supplied by Phonak slimwires, because they are there. However, you could use copper wire or iron: At least those are available at a lot of cross sections.) Let the stick only stick out for one ( or two) millimeter(s), because that side goes into your ears. Wait 5 minutes. Done.