I have a boston (he is so awesome)... luckily my boyfriend has a job at a bar and works evenings so we were able to take him out a lot when he was young. Normally he was crated about 1 hour when he was young. As he got older, we crated him 4 - 5 hours at a time occasionally. He is no longer crated at all. The longest we have left him (one time, for which I will feel eternally guilty) was last summer for 12 hours. If we plan on being gone more than 6 hours, or think there is that risk, we take him somewhere else where people can take care of him.
Do you have a friendly neighbor that could let him out about half way through the day? Somebody that leaves for work a couple hours later than you? Or gets home a couple hours earlier? I could see this as an ideal thing for a 7th/8th/9th grade neighbor that wants to earn a little cash for spending money. Maybe $10/week or something. Just a thought:)