Unfortunately, I have no experience with Boelen's. All I can say is I have never had a morelia in my collection that experience a 2 ft increase in length after the age of 4. It's impossible to say if this snake is truly undersized, 7 ft is well within normal parameters for this species I believe. I did acquire a pair of JCP some years ago that were severally undersized for their age, 3 year olds that looked like yearlings, they never attained normal JCP size, but did experience considerable growth both in length and girth in my care. I'd guess they increased their length by probably 1/3 once put on a proper feeding regime. So if this snake is truly undersized due to a minimalist diet, I guess there's hope.