Wheat yeasts, including 3068 and 3056 will kick up a lot more krausen than ale or wine yeasts. However, you dont necessarily need a huge amount of head space. Wheat yeast krausen is really foamy and will often expand to fill whatever available space you give it, but its fairly light and compresses easily. So you can use a blowoff tube that goes into a tall column of water, like a wine bottle. This will increase the pressure in the fermentation vessel, which will push the krausen down.
Below are 4 wheat batches from last year, where the krausen was about as heavy as it ever gets. As you can see, if it gets really heavy, you might have to change a blowoff bottle to keep from attracting fruit flies, but you wont lose much juice. I fill 6 gallon carboys to 5.5 gallons, which ensures that there will be at least 5 gal to completely fill the secondary after the crash. Most of the time, the krausen doesnt even reach the blowoff tube (like the one on the far right).