Dubias are the best nutrition for your gecko. Crickets are almost as good. Dubias don't stink like a box of crickets. Dubias don't carry parasites. Dubias look like they have very hard shells, but actually they are extremely soft...pick one up and you'll see. I don't recall reading about any impaction from dubias. Actually, the main reason geckos get impacted is from folks using moss, mulch, or sand substrates. But standard feeder bugs should never cause impaction.
I do know my gecko (a little over a year old) can chomp down a full grown, large dubia roach no problem at all. He looks like he's almost gonna choke on it, but he chews it up. Sometimes one large roach fills him up. Geckos can eat fairly decent size bugs. They gulp it down like a snake. Slowly pulling it in and down.
If you only have one gecko DO NOT bother doing a colony. He'll never eat that much. I can buy 24 dubias and they can last a long time. It's best to get in the habit of feeding your gecko a variety of bugs. This way he won't become too picky and he'll be getting a wide spectrum of nutrition.