Mileage Run Deals - LHR-TPA on UA. Any tips?

Hi there,
Not a mileage run in absolute sense but a request to help maximise a trip:

I have to travel LHR-TPA for a conference from the 19-22 Nov. A standard LHR-TPA (with a Saturday night stay) RT on UA prices up at GBP 306.

Obviously from posting it here, I want to maximise my miles. I am going to use the weekend before the conference to visit some friends near SFO. Here is my idea, can anybody suggest something better? Note: TPA-ORD-IAD almost quadruples the total price compared to TPA-IAD direct. Oh, I really prefer the daytime return transatlantic which is why I'm not connecting via EWR/BOS/etc...


16/11. LHR-ORD-LAX-SJC
18/11. SJC-SBA-DEN-TPA
23/11. TPA-IAD
24/11. IAD-LHR

Total cost: GBP 336
Total miles: 3953+1745+500+500+916+1506+810+3677 = 13607
With 1P bonus, on-line booking and UK credit card that gives a total of 31550 miles. With todays exchange rate that works out at 1.6 US cents/mile.

Can anybody offer any suggestions to push this even further without significant prices increases?

Many thanks,
Jason