Drillman... don't use the basket.
OK, I say that with a sincere concern for your safety, but, here is the deal as far as OSHA is concerned.
This type of device cannot be used with a forklift unless the manufacturer of the forklift has approved the use of the basket with their equipment. Where do I get this? The regulation cited by OSHA is: 29 CFR 1910.178(a)(4).
Here is the "stock" information that I put into my reports when I find one of these on a jobsite:
Remove the manlift basket/work platform from service until you obtain the powered industrial truck (e.g., forklift) manufacturer's written approval for its continued use. Modifications and additions which affect capacity and safe operation must not be performed by the customer or user without manufacturers prior written approval. Capacity, operation, and maintenance instruction plates, tags, or decals must be changed accordingly.
If the truck is equipped with front-end attachments other than factory installed attachments, the user must request that the truck be marked to identify the attachments and show the approximate weight of the truck and attachment combination at maximum elevation with load laterally centered.
Ensure that if the approval is given that employees are instructed in the capacity and other limitations assigned by the manufacturers of the work platform and lift truck.
All work platforms used for lifting personnel must adhere to the applicable requirements of ASME B56.1-2000 as outlined in paragraphs 4.17.2, 4.17.3, and 7.36.3. Please be aware that OSHA will, in limited circumstances, allow the employer to obtain written approval from a qualified Registered Professional Engineer after receiving no response or a negative response from the powered industrial truck manufacturer. If the manufacturer's response was negative, then the engineer, prior to granting approval for the modification or addition, would need to perform a safety analysis and address all safety and/or structural issues contained in the manufacturer's disapproval.
Even where the addition of a work platform to a powered industrial truck is permitted under §1910.178(a)(4), employers must also address the fall hazards that result from the use of elevated platforms. An employer's failure to prevent or correct, to the extent feasible, fall hazards from elevated work platforms might be citable as a violation of Section 5(A)(1) of the OSHAct. OSHA's evaluation of the existence of a serious, recognized hazard and the availability of feasible means of abatement would include consideration of the relevant provisions of the ASME B56.1-2000 standard.
Most of the information above can be verified through a letter of interpretation that OSHA issued in on this condition. The letter can be reviewed online at: http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=24877
One last thing... you mentioned that you regularly wear "fall protection" in other manlifts. You should be aware that technically you do not want to wear fall protection, you want to wear a restraint device. What's the difference? Well a restraint device prevents you from falling any distance and is usually attached to a lanyard that is no more than 3' in length. The reason for this is if the anchorage point on the lift will not withstand your fall, the entire lift may be toppled by the force of your body when your lanyard bottoms out. Or you may swing into the side of the lift. I am aware of at least one fatality where an employee wearing a 6-foot lanyard fell from the basket and swung into the side of the truck.
Here is a link to another letter that briefly explains this concept and the difference between "fall protection", "restraint devices" and "positioning devices". http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=24360
Sorry for the length of the post, but, this is kinda complicated. Please let me know if this answers your question.