PIP Mobility

I was reading somewhere about the rules and regs regarding PIP and the moving about question.
It stated 'to stand upright on two feet and walk aided or unaided 20,50 metres'. My question is the 'stand upright' bit! Due to my severe scoliosis and kyphosis I am now unable to stand upright, I am continuously bent and look at the floor when walking. I have to stop every 10 metres or so so that i can stretch just for a few monents to determine where I am. I am usually in pain most of the day. My car is my lifeline. When sat in a chair I look normal, when I stand I give a totally different picture.
Would I be able to argue this point at a tribunal if I were to be unsuccessful in the DLA/PIP changeover.

Sorry Gordon, but this is where I found the info on the word what 'to stand 'means.

'Definitions
Terms used in the PIP descriptors are defined in regulations and, in relation to Activity 2, are -

"aided" means with - (a) the use of an aid or appliance; or (b) supervision, prompting or assistance;
"aid or appliance" - (a) means any device which improves, provides or replaces C's impaired physical or mental function; and (b) includes a prosthesis;
"assistance" means physical intervention by another person and does not include speech;
"prompting" means reminding, encouraging or explaining by another person;
"stand" means stand upright with at least one biological foot on the ground;
"supervision" means the continuous presence of another person for the purpose of ensuring C’s safety;
"unaided" means without - (a) the use of an aid or appliance; or (b) supervision, prompting or assistanc