IMO, this is not a great plan.
1) In general, using aero bars makes handling a bike much more difficult. Combine that with the responsiveness of the Dahon Speed bikes (due to wheel size and geometry), the bike will be very hard to handle.
2) The handlepost on a Dahon is too tall to make putting so much weight on it advisable.
3) Since the Dahon Speed has minimal positional adjustment, it will be difficult to get aerobars in the optimal spot.
Clip-on aero bars won't permanently cripple the fold. However they need to be pretty tight (you're in big trouble if they slip), need to be adjusted properly and are usually attached using allen screws (not QR's). I.e. you can't just pop it off every time you want to fold, without investing significant time to the process.
There are very few folders or 20" wheeled bikes where aero bars are feasible, e.g. Air Friday and maybe more solid and adjustable bikes like the Swift, Pacific Reach, Dahon mini-bikes (e.g. Hammerhead).
If you're out for speed, better options include:
2) Lower the handlebars
4) Faster / slicker / high pressure tires
6) Using a different bike (if you have the budget and/or space)
7) Yet more training
8) Scrupulously cleaning the drivetrain