What is the LTR-WP visa stamping process after receiving BOI Endorsement Approval, and can the application be submitted prior to entering Thailand?

I have a question about the LTR-WP visa procurement process AFTER one has received Endorsement Approval from BOI and one wants to travel to Bangkok to get it stamped on the passport.

We want to fill out the on-line form on LTR's webiste but one of the fields to be filled in the form asks for the entry date and duration of stay, which will be based on the STAMP the immigration puts when we land. Now our current plan is to be in BKK on Nov 13th which is already 55 days out from today.

To complicate the matters, the Endorsement Qualification email also said that we have 60days from the date of the Endorsement to fill out this form and submit it for getting a visa date issued by the immigration/visa service. This leaves us a VERY short window of 4-5 days upon arrival to submit any additional documents they'll tell us only after our submisision.

Has anyone gotten an LTR-WP visas and had to travel to Bangkok to get it issued? If so, I would like an opportunity to understate the exact process. TIA

EDIT: Sorry, I have been QUALIFIED for Endorsement by the BOI but have NOT received the formal Endorsement Letter. Before that step I need to fill out an application online and my question is can that be filed before I enter Thailand and if so, what should i fill in the field where it asks "Duration of Stay in Thailand" coz my understanding is that the duration will be determined at the port of entry (BKK) when I get there. Is that correct, or can I put 60d because I hold a passport that allows me visa-free entry for 60d?